Morbidity and Mortality Weekly Report
 

Recommendations and Reports October 18, 2002 / Vol. 51 / No. RR-15
 

Screening Tests To Detect Chlamydia trachomatis
 

and Neisseria gonorrhoeae Infections — 2002
 

INSIDE: Continuing Education Examination 

Centers for Disease Control and Prevention
 Centers for Disease Control and Prevention

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MMWR
 

The MMWR series of publications is published by the 

Epidemiology Program Office, Centers for Disease 

Control and Prevention (CDC), U.S. Department of 

Health and Human Services, Atlanta, GA 30333. 

SUGGESTED CITATION 

Centers for Disease Control and Prevention. 

Screening Tests To Detect Chlamydia trachomatis and 

Neisseria gonorrhoeae Infections — 2002. MMWR 

2002;51(No. RR-15): [inclusive page numbers]. 

Centers for Disease Control and Prevention 

Julie L. Gerberding, M.D., M.P.H. 

Director 

David W. Fleming, M.D. 

Deputy Director for Science and Public Health 

Dixie E. Snider, Jr., M.D., M.P.H. 

Associate Director for Science 

Epidemiology Program Office 

Stephen B. Thacker, M.D., M.Sc. 

Director 

Office of Scientific and Health Communications 

John W. Ward, M.D. 

Director
 

Editor, MMWR Series
 

Suzanne M. Hewitt, M.P.A. 

Managing Editor 

C. Kay Smith-Akin, M.Ed. 

Project Editor 

Lynda G. Cupell
 

Malbea A. Heilman
 

Beverly J. Holland
 

Visual Information Specialists 

Quang M. Doan
 

Erica R. Shaver
 

Information Technology Specialists 

On the Cover: Methods to detect Chlamydia trachomatis 

or Neisseria gonorrhoeae include microscopy (Gram-stain 

negative diplococci, lower-left), culture (intracellular 

inclusions, upper-left), and nucleic acid detection tests 

(DNA helix, right). 

CONTENTS
 

Introduction ......................................................................... 1
 

Testing Technologies ............................................................ 3
 

Laboratory-Based Tests...................................................... 3
 

Point-of-Care Tests ............................................................ 6
 

C. trachomatis and N. gonorrhoeae Test Performance 

When Used for Screening .................................................. 6 

C. trachomatis Tests for Screening Women and Men .......... 7
 

N. gonorrhoeae Tests for Screening Women and Men ........ 8
 

Selecting Screening Tests ..................................................... 9
 

Performance Perspective for Selecting Screening Tests ....... 9
 

Additional Considerations in Selecting a Screening Test .. 12
 

Methods To Enhance Performance or Reduce Costs ......... 14
 

Collecting, Transporting, and Storing Specimens ................ 19
 

Collecting and Transporting Specimens for Screening...... 19
 

Collecting Specimens for Indications
 

Other Than Screening ................................................. 21
 

Laboratory Implementation of NAATS ................................ 21
 

Test of Cure, Treatment Failure, and Antimicrobial
 

Resistance ...................................................................... 22
 

Sexual Assault and Sexual Abuse ....................................... 22
 

References ......................................................................... 23
 

Appendix A........................................................................ 28
 

Appendix B ........................................................................ 31
 

Appendix C ....................................................................... 34
 

Appendix D ....................................................................... 35
 

Appendix E ........................................................................ 37
 

Appendix F ........................................................................ 38
 

Continuing Education Examination ................................. CE-1
 

This report is also available at http://www.cdc.gov/std/labguidelines. 

A limited number of copies can be ordered at that website. 
Vol. 51 / RR-15 Recommendations and Reports 1 

Screening Tests To Detect Chlamydia trachomatis 

and Neisseria gonorrhoeae Infections — 2002 

Prepared by
 

Robert E. Johnson, M.D.1
 

Wilbert J. Newhall, Ph.D.1
 

John R. Papp, Ph.D.2
 

Joan S. Knapp, Ph.D.2
 

Carolyn M. Black, Ph.D.2
 

Thomas L. Gift, Ph.D.1
 

Richard Steece, Ph.D.3
 

Lauri E. Markowitz, M.D.1
 

Owen J. Devine, Ph.D.1
 

Cathleen M. Walsh, Dr.P.H.1
 

Susan Wang, M.D.1
 

Dorothy C. Gunter, M.P.H.1
 

Kathleen L. Irwin, M.D.1
 

Susan DeLisle, M.P.H.1
 

Stuart M. Berman, M.D.1
 

1

Division of Sexually Transmitted Diseases Prevention
 

National Center for HIV, STD, and TB Prevention, CDC
 2

Division of AIDS, STD, and TB Laboratory Research
 

National Center for Infectious Diseases, CDC
 

3

Association of Public Health Laboratories
 

Washington, D.C.
 

Summary 

Since publication of CDC’s 1993 guidelines (CDC. Recommendations for the prevention and management of Chlamydia 

trachomatis infections, 1993. MMWR 1993;42[No. RR-12]:1–39), nucleic acid amplification tests (NAATs) have been 

introduced as critical new tools to diagnose and treat C. trachomatis and Neisseria gonorrhoeae infections. NAATs for 

C. trachomatis are substantially more sensitive than previous tests. When using a NAAT, any sacrifice in performance when urine 

is substituted for a traditional swab specimen is limited, thus reducing dependence on invasive procedures and expanding the 

venues where specimens can be obtained. NAATs can also detect both C. trachomatis and N. gonorrhoeae organisms in the same 

specimen. However, NAATs are usually more expensive than previous tests, making test performance from an economic perspective 

a key consideration. 

This report updates the 1993 guidelines for selecting laboratory tests for C. trachomatis with an emphasis on screening men 

and women in the United States. (In this report, screening refers to testing persons in the absence of symptoms or signs indicating 

C. trachomatis or N. gonorrhoeae infection.) In addition, these guidelines consider tests from an economic perspective and 

expand the previous guidelines to address detection of N. gonorrhoeae as well as C. trachomatis infections. Because of the 

increased cost of NAATs, certain laboratories are modifying manufacturers’ procedures to improve test sensitivity without incurring the full cost associated with screening with a NAAT. Such approaches addressed in these guidelines are pooling of specimens 

before testing with a NAAT and additional testing of specimens whose non-NAAT test result is within a gray zone. This report also 

addresses the need for additional testing after a positive screening test to improve the specificity of a final diagnosis. 

To prepare these guidelines, CDC staff identified pertinent concerns, compiled the related literature published during 1990 or 

later, prepared tables of evidence, and drafted recommendations. Consultants, selected for their expertise or disciplinary and 

organizational affiliations, reviewed the draft recommendations. These final guidelines are the recommendations of CDC staff 

who considered contributions from scientific consultants. These guidelines are intended for laboratorians, clinicians, and managers who must choose among the multiple available tests, establish standard operating procedures for collecting and processing 

specimens, interpret test results for laboratory reporting, and counsel and treat patients. 

The material in this report originated in the National Center for HIV,
 

STD, and TB Prevention, Harold W. Jaffe, M.D., Acting Director, and the Introduction
 Division of Sexually Transmitted Diseases Prevention, Harold W. Jaffe,
 

M.D., Acting Director; and the National Center for Infectious Diseases,
 An estimated 3 million Chlamydia trachomatis infections occur

James M. Hughes, M.D., Director, and the Division of AIDS, STD, and annually among sexually active adolescents and young adults in
 

TB Laboratory Research, Jonathan E. Kaplan, M.D., Acting Director.
 the United States (1). The majority of persons with C. trachomatis 
2 MMWR October 18, 2002 

infection are not aware of their infection because they do not 

have symptoms that would prompt them to seek medical care 

(2). Consequently, screening is necessary to identify and treat 

this infection. 

Untreated, C. trachomatis infections can lead to serious complications. In certain studies, <40% of women with untreated 

C. trachomatis infections experience pelvic inflammatory disease (PID) (3,4). Of these, the majority have symptoms that 

are too mild or nonspecific for them to seek medical treatment. Regardless of symptom severity, the consequences of 

PID are severe. Of those with PID, 20% will become infertile; 

18% will experience debilitating, chronic pelvic pain; and 9% 

will have a life-threatening tubal pregnancy (5). C. trachomatis 

infection during pregnancy leads to infant conjunctivitis and 

pneumonia and maternal postpartum endometritis. 

Among men, urethritis is the most common illness resulting from C. trachomatis infection. Complications (e.g., epididymitis) affect a minority of infected men and rarely result in 

sequelae. Among men who engage in receptive anal intercourse, 

the rectum is a common site of C. trachomatis infection. Rectal infections are usually asymptomatic, but can cause symptoms of proctitis or proctocolitis. C. trachomatis can cause 

conjunctivitis among adults and is a cause of sexually acquired 

reactive arthritis.* 

Estimated tangible costs of C. trachomatis illness in the 

United States exceed $2.4 billion annually (6). Also critical 

are the intangible costs, including the psychological and emotional injury caused by infertility and ectopic pregnancy. 

As of December 2000, all 50 states and the District of 

Columbia had enacted laws requiring the reporting of 

C. trachomatis cases. In 2001, C. trachomatis infections were 

the most commonly reported communicable infections, with 

a total of 783,242 reports to CDC (7). Rates of C. trachomatis 

infection for women are highest for adolescents (2,536/ 

100,000 among women aged 15–19 years) and young adults 

(2,447/100,000 among women aged 20–24 years). These age 

groups had the highest rates of infection for men as well, 

although the peak rate occurred among men aged 20–24 years 

(605/100,000). 

Reported rates of C. trachomatis infections have risen significantly during 1987–2001 (51–278 cases/100,000 persons) 

(7). This increase is probably caused by a combination of factors, including an increased awareness of the need to screen 

women for C. trachomatis infection, resulting in the initiation 

of screening programs in both public and private health-care 

settings, improvement in the sensitivity of diagnostic tests, 

improved surveillance and reporting systems, and continued 

high infection rates. 

* These guidelines do not address trachoma and lymphogranuloma venereum, 

which rarely occur in the United States. 

Introduction of large-scale screening programs (e.g., one 

initiated in the Department of Health and Human Services 

Region X [Alaska, Idaho, Oregon, and Washington] family 

planning clinics in 1988) have been followed by a reduction 

in C. trachomatis positivity rates by <60% (7–9). C. trachomatis 

screening programs have been initiated throughout the United 

States that are based on such demonstration projects. 

In 2001, Neisseria gonorrhoeae was second in frequency only 

to C. trachomatis among reported communicable infections 

in the United States, with 361,705 reported cases (7). The age 

distribution of N. gonorrhoeae infections is similar to that for 

C. trachomatis infections. Also similar to C. trachomatis, 

uncomplicated N. gonorrhoeae infection is usually confined to 

the mucosa of the cervix, urethra, rectum, and throat; 

N. gonorrhoeae infection is often asymptomatic among females; 

and, if untreated, N. gonorrhoeae infection can lead to PID, 

tubal infertility, ectopic pregnancy, and chronic pelvic pain 

(10). N. gonorrhoeae usually causes symptomatic urethritis 

among males, and occasionally results in epididymitis. Rarely, 

local infection disseminates to cause an acute dermatitis tenosynovitis syndrome, which can be complicated by arthritis, 

meningitis, or endocarditis (10). Also, similar to C. trachomatis, 

N. gonorrhoeae can be acquired at birth. N. gonorrhoeae neonatal infection can cause severe conjunctivitis, which can 

result in blindness if untreated and, rarely, sepsis with associated meningitis, endocarditis, or arthritis. After the introduction of a national control program in the mid-1970s, the overall 

rate of reported N. gonorrhoeae infection had declined by 74% 

during 1975–1997 (7,11). However, the rate increased by 8.1% 

during 1997–1999, followed by a limited decline in 2000–2001. 

Culture testing for C. trachomatis and N. gonorrhoeae has 

been the reference standard against which all other tests have 

been compared. However, other tests have been needed 

because culture methods for C. trachomatis are difficult to standardize, technically demanding, and expensive. Culture for 

either agent is associated with problems in maintaining the 

viability of organisms during transport and storage in the 

diverse settings in which testing is indicated. Thus, diagnostic 

test manufacturers have developed nonculture tests that do 

not require viable organisms, including tests that can be 

automated. The first nonculture screening tests for 

C. trachomatis and N. gonorrhoeae included enzyme immunoassays (EIAs), which detect specific chlamydial or gonococcal antigens, and direct fluorescent antibody (DFA) tests 

for C. trachomatis, which use fluorescein-conjugated monoclonal antibodies that bind specifically to bacterial antigen in 

smears. These antigen-detection tests were followed by nucleic 

acid hybridization tests, which detect C. trachomatis-specific 

or N. gonorrhoeae-specific deoxyribonucleic acid (DNA) or 
Vol. 51 / RR-15 Recommendations and Reports 3 

ribonucleic acid (RNA) sequences. With the availability of 

these nonculture tests, screening programs for C. trachomatis 

were initiated, and screening programs for N. gonorrhoeae 

began to change from culture to using the more convenient 

and, in remote settings, more reliable nonculture methods. 

The primary drawback of these tests, chiefly for C. trachomatis, 

is that they fail to detect a substantial proportion of infections 

(12–23). Consequently, a new generation of nonculture tests, 

called nucleic acid amplification tests (NAATs), were developed that amplify and detect C. trachomatis-specific or 

N. gonorrhoeae-specific DNA or RNA sequences. These tests 

are substantially more sensitive than the first generation 

nonculture tests (12–23). 

These guidelines are intended to assist laboratorians, clinicians, and managers 1) select screening tests for C. trachomatis 

or N. gonorrhoeae from the complex array of tests available; 

2) establish standard operating procedures for collecting, processing, and analyzing specimens; and 3) interpret test results 

for laboratory reporting, counseling, and treating patients. The 

guidelines were developed through literature reviews and 

extended consultation with non-CDC sexually transmitted 

disease (STD) specialists. 

Testing Technologies 

The following discussion is a review of the complex array of 

technologies now available for laboratory diagnosis of 

C. trachomatis and N. gonorrhoeae infections. For this report, 

technologies are subdivided into those that are designed for 

1) batch testing in a laboratory or 2) point-of-care testing as 

single tests or a limited number of tests performed while 

patients await results. Laboratory-based tests include culture, 

NAATs, nucleic acid hybridization and transformation tests, 

EIAs, and DFA tests. Point-of-care tests have long included 

the Gram-stained smear for N. gonorrhoeae. Point-of-care tests 

for C. trachomatis include solid-phase EIAs and a solid-phase 

optical immunoassay. The leukocyte esterase test (LET) is a 

dipstick test that is applied to urine specimens to screen for 

urinary tract inflammation (see Methods To Enhance Performance or Reduce Costs). Personnel, quality assurance, and 

quality control requirements relating to the use of all tests for 

medical care are published in the Clinical Laboratory Improvement Amendments of 1988 (CLIA) regulations (24) and are 

linked to testing complexity. 

Laboratory-Based Tests 

Culture Tests 

C. trachomatis Culture. Cell culture for C. trachomatis 

involves inoculating a confluent monolayer of susceptible cells 

with an appropriately collected and transported specimen. 

After 48–72 hours of growth, infected cells develop characteristic intracytoplasmic inclusions that contain substantial 

numbers of C. trachomatis elementary and reticulate bodies. 

These unique inclusions are detected by staining with a 

fluorescein-conjugated monoclonal antibody that is specific 

for the major outer membrane protein (MOMP) of 

C. trachomatis. 

Cell culture methods vary among laboratories, leading to 

probable substantial interlaboratory variation in performance 

(25). For example, because of a larger inoculum and reduced 

risk of cross-contamination, the shell vial method of culture is 

more sensitive and specific than the 96-well microtiter plate 

method (26,27). In certain laboratories, higher sensitivities 

are obtained by performing a blind pass in which an inoculated cell monolayer is allowed to incubate for 48–72 hours, 

after which the monolayer is disrupted and used to inoculate 

a fresh monolayer that is stained after another cycle of growth (28). 

Tissue culture detection of C. trachomatis is highly specific 

if a C. trachomatis-MOMP-specific stain is used, because 

stained C. trachomatis inclusions have a unique appearance. 

Less specific inclusion-detection methods using EIA, iodine, 

and Giemsa are not recommended (29,30). Certain CDC 

consultants believe that commercial stains employing monoclonal antibodies directed against lipopolysaccharide (LPS), 

which are genus-specific rather than species-specific, are more 

sensitive and more economical than species-specific monoclonal antibody stains directed against MOMP. Such stains 

might be suitable for routine use, but a species-specific stain 

would be preferable in situations requiring increased specificity. 

The high specificity of cell culture and ability to retain the 

isolate make cell culture the first choice when the results will 

be used as evidence in legal investigations. In addition, cell 

culture is the only method by which a clinical isolate can be 

obtained for antimicrobial susceptibility testing. The relatively 

low sensitivity, long turnaround time, difficulties in standardization, labor intensity, technical complexity, stringent transport requirements, and relatively high cost are the primary 

disadvantages of cell culture isolation of C. trachomatis. Additional information regarding cell culture for C. trachomatis is 

available elsewhere (14,28,31). 

N. gonorrhoeae Culture. Methods of gonococcal culture 

have been well-described elsewhere (12,32). Specimens are 

streaked on a selective (e.g.,Thayer-Martin or Martin-Lewis) 

or nonselective (e.g., chocolate agar) medium if specimens are 

from nonsterile or sterile sites, respectively. Inoculated media 

are incubated at 35o

C–36.5oC in an atmosphere supplemented 

with 5% CO2 and examined at 24-hour intervals for <72 hours. 

Culture media for N. gonorrhoeae isolation include a base 

medium supplemented with chocolatized equine or bovine 
4 MMWR October 18, 2002 

blood to support the growth of the gonococcus; selective 

media differ from routine culture media in that they contain 

antimicrobial agents (i.e., vancomycin, colistin, and an antifungal agent), which inhibit the growth of other bacteria and 

fungi. Supplemental CO2 can be supplied by a CO2 incubator, candle-extinction jar, or CO2-generating tablets. 

A presumptive identification of N. gonorrhoeae isolates recovered from a genital specimen on selective medium can be 

made with a Gram stain and oxidase test. A presumptive identification indicates only that a Gram-negative, oxidase-positive 

diplococcus (e.g., a Neisseria species or Branhamella [Moraxella] 

catarrhalis) has been isolated from a specimen. Certain coccobacilli, including Kingella denitrificans, might appear to be 

Gram-negative diplococci in Gram-stained smears. A confirmed laboratory diagnosis of N. gonorrhoeae cannot be made 

on the basis of these tests alone. A presumptive test result is 

sufficient to initiate antimicrobial therapy, but additional tests 

must be performed to confirm the identity of an isolate as N. 

gonorrhoeae. Culture isolation is also suitable for nongenital 

tract specimens. Using selective media is necessary if the anatomic source of the specimen normally contains other bacterial species. 

The sensitivity of culture can be monitored (i.e., qualitycontrolled) by evaluating results among males with urethral 

discharge. Culture results are compared with results obtained 

by using Gram-stained smear or by using nonselective 

medium. Vancomycin-sensitive strains, which were relatively 

common in certain areas in the past, now appear to be an 

uncommon cause of false-negative cultures (10,12,33,34). 

The advantages of culture are high sensitivity and specificity, low cost, suitability for use with different types of specimens, and the ability to retain the isolate for additional testing. 

Retention of the isolate for additional testing might be indicated for medicolegal purposes, antimicrobial susceptibility 

determination, and subtyping of isolates. The major disadvantage of culture for N. gonorrhoeae is that specimens must 

be transported under conditions adequate to maintain the 

viability of organisms. Another disadvantage is that a minimum of 24–72 hours is required from specimen collection to 

the report of a presumptive culture result. 

NAATs 

The common characteristic among NAATs is that they are 

designed to amplify nucleic acid sequences that are specific 

for the organism being detected. Similar to other nonculture 

tests, NAATs do not require viable organisms. The increased 

sensitivity of NAATs is attributable to their ability to produce 

a positive signal from as little as a single copy of the target 

DNA or RNA. Commercial tests differ in their amplification 

methods and their target nucleic acid sequences. The Roche 

Amplicor® (manufactured by Roche Diagnostics Corporation, 

Basel, Switzerland) test uses polymerase chain reaction (PCR); 

the Abbott LCx® (Abbott Laboratories, Abbott Park, Illinois) 

test uses ligase chain reaction (LCR); and the Becton Dickinson 

BDProbeTecTM ET (Becton, Dickinson and Company, 

Franklin Lakes, New Jersey) test uses strand displacement 

amplification to amplify C. trachomatis DNA sequences in 

the cryptic plasmid that is found in >99% of strains of 

C. trachomatis. The Gen-Probe APTIMATM (Gen-Probe, Incorporated, San Diego, California) assay for C. trachomatis 

uses transcription-mediated amplification (TMA) to detect a 

specific 23S ribosomal RNA target. These nucleic acid amplification methods are also used to detect N. gonorrhoeae. The 

target for the Roche Amplicor test for N. gonorrhoeae is a 201 

base pair sequence within the cytosine methyltransferase gene 

M:Ngo P11. The Abbott LCx test for N. gonorrhoeae detects a 

48 base-pair sequence in the Opa genes, <11 copies of which 

occur per cell, whereas the BDProbeTec ET for N. gonorrhoeae 

detects a DNA sequence that is within the multicopy pilin 

gene-inverting protein homologue. The Gen-Probe APTIMA 

Combo 2 version of TMA detects the 16S ribosomal RNA 

(rRNA) of N. gonorrhoeae. Additional overviews of the various amplification methods can be found in other published 

reports (16,35,36) and in materials available from the manufacturers. 

The majority of commercial NAATs have been cleared† by 

the Food and Drug Administration (FDA) to detect 

C. trachomatis and N. gonorrhoeae in endocervical swabs from 

women, urethral swabs from men, and urine from both men 

and women. In addition, other specimens (e.g., those from 

the vagina [37–50] and eye [51–53]) have been used with 

satisfactory performance, although these applications have 

not been cleared by FDA. Testing of rectal and oropharyngeal 

specimens with NAATs has had limited evaluation and is not 

recommended. 

The ability of NAATs to detect C. trachomatis and 

N. gonorrhoeae without a pelvic examination or intraurethral 

swab specimen (for males) (e.g., by testing urine) is a key 

advantage of NAATs, and this ability facilitates screening males 

and females in other than traditional screening venues (e.g., 

STD and family planning clinics). A disadvantage of NAATs 

is that specimens can contain amplification inhibitors that 

result in false-negative results. Certain manufacturers provide 

† The term cleared is used by the Food and Drug Administration (FDA) to describe 

the process they use to review applications to market the class of diagnostic 

tests that includes C. trachomatis and N. gonorrhoeae tests discussed in these 

guidelines. The term approved is used by FDA to describe a more rigorous 

process they use to review applications to market classes of diagnostic tests that 

involve, for example, higher levels of risk if the test result is erroneous than is 

the case for C. trachomatis or N. gonorrhoeae. 
Vol. 51 / RR-15 Recommendations and Reports 5 

amplification controls to detect inhibition. Selected NAATs 

might be substantially less sensitive than non-NAATs when 

performed on urine than when performed on endocervical 

specimens (54–56) or male urethral swabs (54,56). Although 

not documented by published head-to-head studies, the 

majority of CDC consultants believe that non-NAATs are substantially less sensitive than NAATs when used on urine specimens. The nucleic acid primers employed by commercial 

NAATs for C. trachomatis are not known to cross-react with 

DNA from other bacteria found in humans. However, the 

primers employed by certain NAATs for N. gonorrhoeae might 

cross-react with nongonococcal Neisseria species (54,56,57). 

NAATs are also more susceptible than non-NAATs to falsepositive results because of contamination if strict quality control procedures are not applied. 

Nucleic Acid Hybridization (Nucleic Acid 

Probe) Tests 

Two nucleic acid hybridization assays are FDA-cleared to 

detect C. trachomatis or N. gonorrhoeae: the Gen-Probe PACE® 

2 and the Digene Hybrid Capture® II assays. Both the PACE 

and Hybrid Capture assays can detect C. trachomatis or 

N. gonorrhoeae in a single specimen. The PACE 2C test and 

the Hybrid Capture II CT/GC versions of these tests do not 

differentiate between the two organisms and, when positive, 

should be followed by tests for each organism to obtain an 

organism-specific result. In the Gen-Probe hybridization 

assays, a DNA probe that is complementary to a specific 

sequence of C. trachomatis or N. gonorrhoeae rRNA hybridizes 

with any complementary rRNA that is present in the specimen (58). A competitive probe version of the PACE 2 assay is 

commercially available to augment specificity. In this version, 

the test is repeated on initially positive specimens with and 

without adding an unlabeled probe. The unlabeled probe competitively inhibits binding of the labeled probe; a reduction in 

signal when the assay is performed with the unlabeled probe is 

interpreted as verification of the initial positive test result. 

RNA hybridization probes in the Digene assay are specific 

for DNA sequences of C. trachomatis and N. gonorrhoeae, 

including both genomic DNA and cryptic plasmid DNA (59). 

Technical requirements and expertise necessary for performing nucleic acid hybridization tests are similar to those for the 

EIAs, which are described in this report. One of the advantages of the nucleic acid hybridization tests is the ability to 

store and transport specimens for <7 days without refrigeration before receipt and testing by the laboratory. 

Nucleic Acid Genetic Transformation Tests 

The Gonostat® test (Sierra Diagnostics, Incorporated, 

Sonora, California) uses a gonococcal mutant that grows when 

transformed by DNA extracted from a swab specimen containing N. gonorrhoeae. N. meningitidis causes false-positive 

results (60). The test has received limited evaluation in 

published studies (61–64), which include an evaluation of its 

use with mailed specimens (62). A genetic transformation test 

is not available for detection of C. trachomatis infection. 

EIA Tests 

A substantial number of EIA tests have been marketed for 

detecting C. trachomatis infection. By contrast, the performance and cost characteristics of EIA tests for N. gonorrhoeae 

infection have not made them competitive with culture (32). 

C. trachomatis EIA tests detect chlamydial LPS with a monoclonal or polyclonal antibody that has been labeled with an 

enzyme. The enzyme converts a colorless substrate into a colored product, which is detected by a spectrophotometer. Specimens can be stored and transported without refrigeration and 

should be processed within the time indicated by the manufacturer. One disadvantage of the EIA methods that detect 

LPS is the potential for false-positive results caused by crossreaction with LPS of other microorganisms, including other 

Chlamydia species (28,30,65,66). Manufacturers have developed blocking assays that verify positive EIA test results. The 

test is repeated on positive specimens with the addition of a 

monoclonal antibody specific for chlamydia LPS. The monoclonal antibody competitively inhibits chlamydia-specific 

binding by the enzyme-labeled antibody; a negative test result 

when using the blocking antibody is interpreted as verification of the initial positive test result. EIA tests should not be 

used with rectal specimens because of cross-reactions with fecal bacteria. 

DFA Tests 

Depending on the commercial product used, the antigen 

that is detected by the antibody in the C. trachomatis DFA 

procedure is either the MOMP or LPS molecule. Specimen 

material is obtained with a swab or endocervical brush, which 

is then rolled over the specimen well of a slide. After the slide 

has dried and the fixative applied, the slide can be stored or 

shipped at ambient temperature. The slide should be processed 

by the laboratory in <7 days after the specimen has been 

obtained. Staining consists of covering the smear with 

fluorescein-labeled monoclonal antibody that binds to 

C. trachomatis elementary bodies. Stained elementary bodies 

are then identified by fluorescence microscopy. Only 

C. trachomatis organisms will stain with the anti-MOMP 

antibodies used in commercial kits. The anti-LPS monoclonal 

antibodies used in certain commercial kits can cross-react with 

nonchlamydial bacterial species, as well as with LPS of 

C. pneumoniae and C. psittaci. DFA with a C. trachomatisspecific anti-MOMP monoclonal antibody is considered 

to be highly specific, when performed by an experienced 
6 MMWR October 18, 2002 

microscopist. An additional advantage of DFA is that the 

quality of endocervical smears can be assessed by checking for 

the presence of columnar cells (see Collecting and Transporting Specimens for Screening). DFA requires that the laboratorian be competent in fluorescent microscopy and adequately 

trained in identifying fluorescein-stained C. trachomatis 

elementary bodies. DFA is best suited for laboratories that 

test a limited number of specimens, because the procedure is 

fatiguing and time-consuming. DFA tests have not been 

established as an initial test for the direct detection of 

N. gonorrhoeae in clinical specimens. 

Serology Tests 

Serology has limited value in testing for uncomplicated genital C. trachomatis infection and should not be used for screening because previous chlamydial infection frequently elicits 

long-lasting antibodies that cannot be easily distinguished from 

the antibodies produced in a current infection. More specific 

information regarding serologic assays for C. trachomatis antibody has been reported elsewhere (14). A serologic screening 

or diagnostic assay is not available for N. gonorrhoeae. 

Point-of-Care Tests 

C. trachomatis Point-of-Care Tests 

Tests for C. trachomatis have been developed that can be 

performed within 30 minutes, do not require expensive or 

sophisticated equipment, and are packaged as single units. The 

results are read qualitatively. These so-called rapid or stat tests 

can offer advantages in physicians’ offices, small clinics and 

hospitals, detention centers, and other settings where results 

are needed immediately (e.g., when decisions need to be made 

regarding additional testing or treatment while the patient is 

still present). These tests are classified under CLIA as tests of 

moderate complexity (24). Accordingly, personnel standards, 

quality control, quality assurance, and proficiency testing 

requirements apply when performing FDA-cleared 

C. trachomatis tests that are rapid enough to qualify as pointof-care tests. In addition, these tests are usually less sensitive 

and more expensive than laboratory-based C. trachomatis tests 

that require longer to perform. Similar to EIAs, these tests use 

antibodies against LPS that detect all three Chlamydia species 

that infect humans and are subject to the same potential for 

false-positive results caused by cross-reactions with other 

microorganisms. A point-of-care test should not be selected if 

it is performed in a laboratory after the patient’s visit. Such 

use of point-of-care tests is inappropriate because sensitivity 

and specificity are typically less, controls less rigorous, and 

costs higher than for tests designed for laboratory use (67). 

Gram Stain for N. gonorrhoeae 

Gram stain is a key tool for the diagnosis of gonococcal 

urethritis in men, but its application to screening is limited 

because of the requirement for an intraurethral swab specimen if discharge is not present at the urethral meatus. A Gram 

stain for the presumptive diagnosis of N. gonorrhoeae infection is performed on thin smears of urethral exudate from 

men and is presumptively positive if the smear contains typical Gram-negative diplococci within polymorphonuclear 

(PMN) leukocytes. Unfortunately, other Neisseria species have 

a similar appearance. Although commensal Neisseria species 

are not normal flora of anogenital sites, isolates of Neisseria 

meningitidis and nonpathogenic Neisseria species have been 

reported occasionally from anogenital sites among both men 

and women (12). 

As a point-of-care test, Gram stain is most reliable for the 

presumptive identification of N. gonorrhoeae in urethral exudates from men. The sensitivity and specificity of a Gram stain 

for males with symptomatic urethritis are comparable to culture isolation followed by oxidase testing and Gram staining 

of the isolate (32,68,69). Gram-negative extracellular diplococci without any intracellular diplococci might be observed 

in smears from men with early symptomatic infections. The 

sensitivity of Gram stain for males with asymptomatic urethral infection has not been determined. Gram-negative 

intracellular diplococci might be observed with certain infections 

caused by nongonococcal Neisseria species (e.g., N. cinerea). 

The sensitivity of Gram stains of endocervical specimens is 

lower than for urethral specimens from men with symptomatic gonorrhea (10,32,69), and adequate specificity requires a 

skilled microscopist. For these reasons, Gram stain is not recommended for testing for N. gonorrhoeae infection among 

women. Gram stains of pharyngeal specimens are not recommended because N. meningitidis and commensal Neisseria species colonize the pharynx (12). As with point-of-care tests for 

C. trachomatis, the Gram-stained smear is classified under CLIA 

as a moderate complexity test for urethral and endocervical 

specimens (24). Gram stains from all other body sites are categorized as high complexity. A trained laboratorian is required 

for preparing and reading high-complexity Gram-stained smears. 

C. trachomatis and N. gonorrhoeae
 

Test Performance When Used
 

for Screening
 

Numerous evaluations of C. trachomatis and N. gonorrhoeae 

tests when used for screening have been published. NAAT 

sensitivities have consistently exceeded the sensitivities of 

non-NAATs. However, the majority of published estimates of 
Vol. 51 / RR-15 Recommendations and Reports 7 

test performance are uncertain because of probable bias from 

1) misclassification of study subjects’ infection status by reference standard tests; 2) using reference standard tests that are 

more suitable for determining whether a study subject is 

infected at one anatomic site (e.g., the endocervix) versus 

determining whether the study subject is infected at any anatomic site; and 3) predominance of studies of female and symptomatic male patients from STD clinics who might not be 

representative of populations who would be targeted for screening. Estimates of the differences in the performance of NAATs 

and non-NAATs are also uncertain because only a limited 

number of evaluations have been conducted that evaluated 

the two sets of tests by using the same set of study subjects 

(i.e., a head-to-head study). 

Identifying a suitable standard for classifying study subjects 

with respect to true infection status has been difficult. Customary reference standards (e.g., culture) are highly specific 

but lack sensitivity. When such standards are used, evaluated 

test specificity is probably underestimated. Truly infected subjects who are misclassified as uninfected by the reference standard are more likely to be determined positive (and thus, 

inappropriately considered falsely positive) by the evaluated 

test than are the uninfected subjects. Misclassification of evaluated test results as false-positives occurs more frequently if the 

evaluated test (e.g., a NAAT) is more sensitive than the reference test (e.g., culture). The majority of evaluators of 

C. trachomatis and N. gonorrhoeae tests have attempted to 

address this problem by using a discrepant analysis procedure. 

This procedure has been strongly contested by statisticians 

and clinical epidemiologists because reference tests are applied 

dependent upon evaluated test results. This dependency contributes a positive bias to estimates of sensitivity and does not 

eliminate ambiguity regarding specificity estimates (70–75). 

Identifying a reference standard that accurately classifies 

study subjects who can be infected at multiple anatomic sites 

is also problematic, chiefly for women. The majority of test 

evaluations for women use an endocervical reference standard 

only. Estimates of evaluated test sensitivity are probably higher 

and specificity lower, when the reference standard for infection is based on a positive result from a single anatomic site 

(e.g., an endocervical swab) rather than from multiple potentially infected sites (e.g., an endocervical swab or urine specimens) (54,76,77). The former standard, which produces 

estimates by using a specimen from one anatomic site, can be 

considered a specimen standard and addresses the concern of 

test performance regarding identification of infection at that 

site. The latter standard can be considered a patient standard. 

The following sections summarize C. trachomatis and 

N. gonorrhoeae test performance on the basis of recent test 

evaluation studies, conducted without discrepant analysis, and 

consultation with specialists in test evaluation. 

C. trachomatis Tests for Screening 

Women and Men 

Sensitivity 

Reviews of screening tests for C. trachomatis conclude that 

sensitivities of commercial NAATs exceed those of non-NAATs 

(14–23). A substantial proportion of the published evaluations of NAATs cited in these reviews have relied on discrepant analysis. However, certain studies permit the calculation 

and comparison of NAAT and non-NAAT sensitivities by 

using culture as an independent reference standard. A fivecenter study reported sensitivities of NAATs for endocervical 

specimens that exceeded the sensitivity of a nonamplified 

nucleic acid hybridization test by 19.7% (95% confidence 

interval [CI] = 12.9%–26.6%) for LCR and 12.4% ( 95% 

CI = 2.1%–22.7%) for PCR (78). The sensitivities of LCR 

and PCR were slightly lower when performed on urine specimens than on endocervical specimens (83.4% versus 91.4% 

and 79.5% versus 84.0% , respectively). The sensitivity of the 

nonamplified hybridization test (71.6%) was similar to that 

reported in an earlier study (75.3%) that compared the hybridization test, three EIAs, and a DFA performed on endocervical swab specimens by using culture as the reference standard 

(79). Sensitivities of the tests evaluated in that study were 

61.9%–75.3%. 

Culture, a NAAT (LCR), and the nonamplified hybridization test have also been compared by using an independent 

reference standard (78). For this evaluation, the reference standard was a positive PCR performed on an endocervical or 

urine specimen. For endocervical swab specimens, the sensitivity of LCR (85.5%) exceeded that of culture (74.7%) by 

10.8% and that of the hybridization test (61.9%) by 23.6%. 

For the urine specimen, the sensitivity of LCR was 80.8%. 

A limited number of studies have used an independent reference standard to compare the sensitivities of tests for detection of C. trachomatis infection in asymptomatic men. One 

five-center study compared LCR and PCR performed on urine 

from asymptomatic males by using culture of intraurethral 

swab specimens as the independent reference standard (80). 

The sensitivities of LCR (84.4%) and PCR (85.4%) were similar. 

The majority of C. trachomatis test evaluation specialists 

consulted for these guidelines believe that the sensitivities of 

the point-of-care tests for C. trachomatis are substantially less 

than the sensitivities of tests with longer processing times. 

However, published studies do not provide a basis for specifying the magnitude of the difference. 
Specificity and Positive Predictive Value 

At the prevalences of C. trachomatis infection typical of populations who are screened (e.g., 2%–10%), the specificity of 

the screening test and the infection prevalence are key variables because they strongly influence the proportion of positive test results that reflect infection. The term used for this 

proportion is the positive predictive value (PPV) (81,82).§ 

At lower prevalences, a positive screening test might need to 

be followed by an additional test to ensure an adequate PPV. 

Published evaluations of NAATs that have used alternative 

target NAATs¶ to perform discrepant analysis have reported 

increased specificities (e.g., exceeding 99.0%–99.5%); such 

reports have addressed NAATs for detection of C. trachomatis 

in endocervical specimens, male urethral specimens, and male 

or female urine. However, statisticians and clinical epidemiologists have criticized these estimation procedures also. Published studies or studies described in package inserts that have 

used DFA to perform discrepant analysis or have used culture 

as the standard without performing discrepant analysis have 

reported specificities of 94.1%–99.5% (75). In 1993, CDC 

reported a similar range of specificities for nonamplified nucleic 

acid probe and EIA tests to detect C. trachomatis (31). This 

report includes a graph of PPVs associated with a test with a 

sensitivity of 85% across a range of test specificities and 

prevalences typical of those reported for C. trachomatis screening applications (Figure). 

§ For example, when a test with a specificity of 99% and a sensitivity of 85% is 

used to screen a population of 10,000 patients with a C. trachomatis prevalence 

of 10% (i.e., 1,000 patients have an infection), an average of 940 test results 

will be positive: 850 patients with a positive result will actually be infected, and 

90 will not be infected (i.e., false-positives). PPV is 850/940 = 0.904. When 

this same test is used to screen 10,000 patients with a chlamydia prevalence of 

only 2% (i.e., 200 patients have an infection), an average of 268 test results 

will be positive: 170 patients will be infected and 98 will not. The PPV is 170/ 

268 = 0.634. 

¶ Published evaluations of commercial NAATs have augmented reference tests 

with an alternative target NAAT performed by the manufacturer that employs 

the same amplification method as the commercial NAAT, except for substitution 

of a different set of primers. 

FIGURE. Positive predictive values of a test with a sensitivity 

of 85% across a range of values of specificity and prevalence 

of infection Positive predictive value (%)

0 

10 

20 

30 

40 

50 

60 

70 

80 

90 

100 

Specificity (%) 

99.5 

99.0 

98.0 

97.0 

1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 

Prevalence (%) 

8 MMWR October 18, 2002 

All positive tests should be considered presumptive evidence 

of infection. Regardless of screening setting, screening location, patient population, and patient characteristics, a falsepositive test result for C. trachomatis can have adverse medical, 

social, and psychological impacts for a patient. In such a case, 

consideration should be given to increasing specificity by performing an additional test after a positive screening test and 

requiring that both the screening test and additional test be 

positive to make a diagnosis of C. trachomatis infection (83). 

PPV of the diagnosis will be increased unless the screening 

and additional tests are falsely positive for the same reasons 

(e.g., both are mislabeled or both cross-react with a 

nonchlamydial organism). However, an additional test does 

not fully resolve all concerns because it might provide a falsenegative result. Because therapy for C. trachomatis is safe and 

should not be delayed, therapy can be offered while awaiting 

additional test results or even if the additional test is negative. 

Patients with positive screening test results require counseling 

regarding both the risks of delaying therapy and the possibility of a false-positive test result. Consideration should be given 

to routine additional testing for persons with positive 

C. trachomatis screening tests when risk factor information or 

actual surveys indicate that the prevalence is low, resulting in 

an inadequate PPV (e.g., <90%) (see Additional Considerations in Selecting a Screening Test and also, Methods To 

Enhance Performance or Reduce Costs). 

N. gonorrhoeae Tests for Screening 

Women and Men 

Sensitivity 

As for C. trachomatis, a substantial proportion of published 

evaluations of NAATs for N. gonorrhoeae have relied on discrepant analysis for calculation of test sensitivities, which might 

have positively biased the estimates. However, a meta-analysis 

of evaluations of N. gonorrhoeae summarizes sensitivity estimates for those studies for which sensitivity estimates could 

be based on culture as the independent reference standard (13). 

By using a culture standard, sensitivities were similar for an 

endocervical swab nucleic acid hybridization test (92.1%) and 

an FDA-cleared NAAT (96.7%). 

Package inserts for NAATs recently cleared by FDA now 

include results of studies conducted by using independent reference standards without employing discrepant analysis. Two 

such package inserts include the results of culture, a previously FDA-cleared NAAT, and the candidate NAAT (84,85). 

When the independent reference standard for infection was a 

previously FDA-cleared NAAT positive on either endocervical swab or urine specimens, the sensitivities of endocervical 

swab culture were less than for the Becton Dickinson 
Vol. 51 / RR-15 Recommendations and Reports 9 

BDProbeTec (83.7% versus 90.2%) and Gen-Probe APTIMA 

(89.3% versus 100.0%) tests; the sensitivities of the NAATs 

were lower when performed on urine than on endocervical 

swabs (78.2% versus 90.2% and 91.7% versus 100.0%, respectively). Compared with tests for C. trachomatis, differences 

in sensitivities among NAATs, nucleic acid hybridization tests 

without nucleic acid amplification, and culture are reduced 

when using endocervical swabs. The exception is that culture 

sensitivity can decline when transport or storage conditions 

compromise organism viability. Gram-stain sensitivity is not 

presented for men because Gram stain of urethral swab smears 

is seldom used for screening men outside STD clinic settings, 

and its performance for that purpose has not been well-evaluated. Gram stain is also not widely used for screening women 

because of decreased sensitivity and variable specificity. 

Specificity and PPV 

As with C. trachomatis, test specificities and prevalences 

among populations screened for N. gonorrhoeae are key determinants of PPV of positive screening test results. Reported 

specificities of N. gonorrhoeae screening tests are similar to 

those for C. trachomatis. Unlike C. trachomatis tests, crossreactivity between N. gonorrhoeae and pathogenic and nonpathogenic Neisseria has been demonstrated for certain NAATs 

(54,56,57). This cross-reactivity has not been reported for the 

Abbott LCx and Gen-Probe APTIMA and PACE 2 tests. 

However, nongonococcal Neisseria are infrequently recovered 

from the genitourinary tract. As with C. trachomatis tests, all 

positive screening tests should be considered presumptive evidence of infection, and routine additional testing after a positive N. gonorrhoeae screening test result would usually be 

indicated when screening among a low-prevalence population. Prevalences of N. gonorrhoeae are usually lower than for 

C. trachomatis, possibly resulting in lower PPVs. The decision 

to screen and conduct additional tests after a positive screening test should be made separately for the two organisms (see 

Additional Considerations in Selecting a Screening Test and 

also, Methods To Enhance Performance or Reduce Costs). 

Selecting Screening Tests 

Multiple considerations affect the selection of a screening 

test. Test sensitivity is emphasized to minimize occurrence of 

false-negative tests, which can result in complications of 

untreated infection and ongoing transmission. However, 

additional considerations might lead to the selection of a different test (see Additional Considerations in Selecting a Screening Test). For example, a goal of maximizing test sensitivity to 

avoid missing the opportunity to treat infected persons might 

warrant tolerating a limited number of false-positive diagnoses. 

However, consideration must also be given to reducing the 

rate and consequences of false-positive tests and to cost (see 

Methods To Enhance Performance or Reduce Costs). This 

report focuses on screening applications of tests for 

C. trachomatis and N. gonorrhoeae infections. This report also 

contains a listing of additional indications for C. trachomatis 

testing and recommendations for choice of test and type of 

specimen (Appendix A); similar information for N. gonorrhoeae 

is also included (Appendix B). 

Performance Perspective for Selecting 

Screening Tests 

On the basis of sensitivity, ease of specimen collection, and 

ability to assess antimicrobial susceptibility (N. gonorrhoeae), 

recommendations for screening women and men for 

C. trachomatis and N. gonorrhoeae genitourinary tract infections are outlined in this section. Recommended screening 

tests will, compared with less sensitive tests, minimize the risk 

for disease sequelae and continued transmission of infections 

as a result of false-negative screening tests. Clinicians should 

be aware of the potential for adverse consequences caused by 

a false-positive test result (e.g., substantial psychosocial or legal consequences); patients with positive results should be 

counseled regarding the potential for false-positive results, and 

additional testing should be considered. Because such a result 

might itself be falsely negative and therapies for C. trachomatis 

and N. gonorrhoeae are safe and effective, treatment might be 

offered while awaiting results from additional testing or even 

if an additional test is negative. At lower prevalences, consideration should be given to routine additional testing after a 

positive screening test. Testing strategies have been proposed 

that can increase specificity and constrain costs by combining 

use of NAATs and non-NAATs. A particularly promising strategy called gray-zone testing involves screening with a nonNAAT and using a lower cutoff value than that established by 

the manufacturer as a criterion for a positive result. A NAAT 

is then performed as an additional test when the non-NAAT 

screening test results are in a zone above the new cutoff value. 

This strategy could achieve greater sensitivity than would be 

provided by using a non-NAAT by itself and greater specificity than would be provided by the separate use of either a 

non-NAAT or a NAAT, and cost less than using a NAAT by 

itself. This strategy might be useful for screening among lower 

prevalence populations for which both PPV and cost of 

detecting an infection are of increased concern. This strategy 

warrants further evaluation (see Additional Considerations in 

Selecting a Screening Test and also, Methods To Enhance Performance or Reduce Costs). 
10	 MMWR October 18, 2002 

Screening Women for C. trachomatis and 

N. gonorrhoeae Genitourinary Tract Infections 

The following recommendations are based on sensitivity, 

ease of specimen collection, and ability to assess antimicrobial 

susceptibility (N. gonorrhoeae) (Box 1). Additional concerns, 

including cost and PPV, are addressed in subsequent sections 

(see Additional Considerations in Selecting a Screening Test 

and also, Methods to Enhance Performance or Reduce Costs). 

C. trachomatis. 

1. A C. trachomatis NAAT performed on an endocervical 

swab specimen provides the highest sensitivity and might 

be preferred if a pelvic examination is acceptable; 

otherwise, a NAAT can be performed on urine. The 

sensitivity of NAATs when using urine to detect 

C. trachomatis in women is similar, or only slightly inferior, 

to their sensitivity when using endocervical swabs (78,86). 

By using urine as a specimen, screening persons in such 

venues as family planning clinics can now be extended 

beyond women undergoing pelvic examinations. 

Screening can be performed also in nontraditional venues 

where pelvic examinations are not performed (e.g., 

schools, jails and detention centers, and street HIV or 

STD outreach programs). 

2. Although less sensitive than NAATs, unamplified nucleic 

acid hybridization tests, EIAs, and DFA performed on 

an endocervical swab specimen are acceptable for 

screening (see Methods To Enhance Performance and 

Reduce Costs). 

BOX 1.Tests used for screening women for genitourinary tract 

infection 

Chlamydia trachomatis 

•	 A nucleic acid amplification test (NAAT) performed 

on an endocervical swab specimen, if a pelvic examination is acceptable; otherwise, a NAAT performed on 

urine. 

•	 An unamplified nucleic acid hybridization test, an enzyme immunoassay, or direct fluorescent antibody test 

performed on an endocervical swab specimen. 

•	 Culture performed on an endocervical swab specimen. 

Neisseria gonorrhoeae 

•	 Culture performed on an endocervical swab specimen. 

If transport and storage conditions are not conducive 

to maintaining the viability of N. gonorrhoeae, a NAAT 

or nucleic acid hybridization test can be performed on 

an endocervical swab specimen. 

•	 A NAAT performed on urine. 

3. C. trachomatis culture performed on an endocervical swab 

specimen is a suitable test for screening. Specificity of 

culture tests is high; however, sensitivity is less than for 

NAATs and variable because of technical complexity, lack 

of standardization, and the challenge of maintaining viable 

organisms. 

No tests have been cleared by FDA for use with vaginal 

specimens. However, studies have assessed using vaginal 

specimens for screening by NAATs (37–49), including vaginal specimens collected by the patient (37,38,40,42,44,47– 

49). The results of these studies are promising. Unless 

manufacturers obtain FDA clearance for this intended use, 

individual laboratories testing vaginal specimens will need 

to conduct a study to establish, rather than just to verify, 

test performance characteristics to satisfy CLIA requirements 

(Appendix C). The sensitivity of non-NAATs with urine or 

vaginal swab specimens is suboptimal. In the case of EIAs, 

specificity with vaginal swab and urine specimens is also 

lower than with endocervical swab specimens (65). Such 

uses of non-NAATs are not recommended. 

N. gonorrhoeae. 

1. An 	N. gonorrhoeae culture test performed on an 

endocervical swab specimen might be preferred on the 

basis of ease of additional testing and on the continuing 

need for antimicrobial-resistance monitoring. When 

culture sensitivity might be compromised because of 

problems in maintaining appropriate transport and 

storage conditions, a NAAT or nucleic acid hybridization 

test can be performed on an endocervical swab specimen. 

2. As with C. trachomatis, screening for N. gonorrhoeae can 

be extended to nontraditional clinical settings by using a 

NAAT performed on urine. The sensitivity of NAATs to 

detect N. gonorrhoeae might be less when using urine than 

when using an endocervical swab specimen (54–56). This 

decrease might be greater for certain NAATs than others 

(54–56). 

As with C. trachomatis, no tests are FDA-cleared for use 

with vaginal specimens, although a study that assessed using patient-obtained vaginal specimens for screening by 

NAATs yielded promising results (50). Unless manufacturers obtain FDA clearance for this intended use, laboratories 

testing vaginal specimens will need to conduct a study to 

establish, rather than just to verify, test performance characteristics to satisfy CLIA requirements (Appendix C). The 

sensitivity of non-NAAT tests to detect N. gonorrhoeae with 

urine or vaginal swab specimens is suboptimal. Such uses of 

non-NAATs are not recommended. 
Vol. 51 / RR-15	 Recommendations and Reports 11 

Screening Men for C. trachomatis 

and N. gonorrhoeae Urethral Infections 

This section includes recommendations for tests for screening men for C. trachomatis and N. gonorrhoeae urethral infections. These recommendations are based on sensitivity, ease of 

specimen collection, and ability to assess antimicrobial susceptibility (N. gonorrhoeae) (Box 2). Additional concerns, 

including cost and PPV, are addressed in subsequent sections 

(see Additional Considerations in Selecting a Screening Test 

and Methods to Enhance Performance or Reduce Costs). 

C. trachomatis. 

1. A NAAT for C. trachomatis performed on an intraurethral 

swab or urine specimen is the preferred test. According 

to STD specialists, NAATs might be more sensitive for 

detecting C. trachomatis infection of asymptomatic men 

when performed on an intraurethral swab specimen than 

on urine, although limited published evaluations 

demonstrate no superiority for swab specimens 

(77,87,88). However, intraurethral swab specimens are 

often unacceptable to males who do not have symptoms 

of urethritis (89–91). NAATs performed on urine to detect 

C. trachomatis have adequate sensitivity to be used for 

screening. The sensitivity of non-NAATs to detect 

C. trachomatis in urine from men is too low for them to 

be recommended for screening. 

2. A non-NAAT or culture for C. trachomatis performed on 

an intraurethral swab specimen is acceptable. 

N. gonorrhoeae. 

1. Culture performed on an intraurethral swab specimen is 

preferred in settings where collecting such specimens is 

acceptable and transport and storage conditions are 

BOX 2. Tests used for screening men for urethral infection 

Chlamydia trachomatis 

•	 A nucleic acid amplification test (NAAT) performed 

on an intraurethral swab specimen if collecting such a 

specimen is acceptable; otherwise, a NAAT performed 

on urine. 

•	 A non-NAAT or culture performed on an intraurethral 

swab specimen. 

Neisseria gonorrhoeae 

•	 Culture performed on an intraurethral swab specimen 

if collecting such a specimen is acceptable and transport and storage conditions are suitable for culture. 

•	 A NAAT or nucleic acid hybridization test performed 

on an intraurethral swab specimen if collecting such a 

specimen is acceptable; otherwise, a NAAT performed 

on urine. 

suitable for culture. Collection of exudate for 

N. gonorrhoeae culture at the urethral meatus without 

insertion of the swab into the urethra is sufficient when 

exudate is present. Culture performed on an intraurethral 

swab specimen is preferred because it facilitates additional 

testing, which is critical for monitoring for antimicrobial 

resistance. When culture sensitivity might be 

compromised because of problems in maintaining 

appropriate transport and storage conditions, a NAAT 

or nucleic acid hybridization test can be performed on 

an intraurethral swab specimen. 

2. A NAAT or nucleic acid hybridization test performed on 

an intraurethral swab specimen or a NAAT performed 

on urine are acceptable tests for screening. Intraurethral 

swab specimens are often unacceptable to males who do 

not have symptoms of urethritis (89–91). In such cases, 

NAATs performed on urine to detect N. gonorrhoeae have 

adequate sensitivity for use in screening. Only a limited 

number of published studies have addressed whether 

NAATs perform better with urethral swab specimens than 

with urine in males with asymptomatic infection. One 

study of asymptomatic males reported that a NAAT was 

substantially less sensitive with urine than with urethral 

swabs; furthermore, NAATs were less sensitive with either 

specimen among males with asymptomatic infection than 

with symptomatic infection (54,56). 

Screening Women or Men with Possible Rectal 

or Pharyngeal Exposure to C. trachomatis 

or N. gonorrhoeae Infection 

Selecting tests for screening for C. trachomatis and 

N. gonorrhoeae rectal or pharyngeal infections is difficult 

because of limited experience with nonculture tests and 

increased potential for cross-reactivity with other organisms 

(Box 3). 

C. trachomatis. 

1. Culture isolation is acceptable for detecting C. trachomatis 

in rectal or pharyngeal swab specimens. A C. trachomatisMOMP–specific stain should be used with culture of 

rectal or pharyngeal specimens to detect C. trachomatis. 

Less-specific inclusion-detection methods by using EIA, 

iodine, Giemsa, or LPS-specific monoclonal antibodies, 

are not recommended (29,30). 

2. DFA can be performed on rectal or pharyngeal swab 

specimens. A C. trachomatis-MOMP-specific stain should 

be used. 

N. gonorrhoeae. 

1. Culture isolation is well established for detecting 

N. gonorrhoeae in rectal and pharyngeal swab specimens. 

After isolation from rectal or pharyngeal specimens of 
12	 MMWR October 18, 2002 

BOX 3. Tests for screening women or men for rectal or 

pharyngeal infection 

Chlamydia trachomatis 

•	 Culture performed on rectal or pharyngeal swab specimens; a C. trachomatis-major outer membrane protein 

(MOMP)-specific stain should be used. 

•	 Direct fluorescent antibody test performed on rectal or 

pharyngeal swab specimens; a C. trachomatis-MOMPspecific stain should be used. 

Neisseria gonorrhoeae 

•	 Culture performed on rectal or pharyngeal swab specimens; a selective medium should be used with additional testing on colonies of typical oxidase-positive, 

Gram-negative diplococci. 

typical oxidase-positive, Gram-negative diplococci on 

selective media, definitive identification of N. gonorrhoeae 

requires additional testing because of the common 

occurrence of other pathogenic and nonpathogenic 

Neisseria species in the pharynx and their occasional 

occurrence in the rectum (12,92,93) (see Methods To 

Enhance Performance or Reduce Costs). 

If the foregoing methods are not available, screening for 

C. trachomatis and N. gonorrhoeae in rectal or pharyngeal specimens is not recommended. Only limited evaluations 

have been published of nonculture tests to detect C. trachomatis 

or N. gonorrhoeae oropharyngeal or rectal infections (32,94,95). 

Additional Considerations in Selecting 

a Screening Test 

In addition to test sensitivity, ease of specimen collection, 

and assessment for antimicrobial susceptibility (N. gonorrhoeae), 

other considerations in choosing a screening test include 1) the 

relatively high cost of NAATs (i.e., economic considerations); 

2) laboratory environmental changes necessary to implement 

NAATs; 3) the need for additional testing to support C. 

trachomatis or N. gonorrhoeae diagnoses; and 4) the likelihood 

of screening-test–positive persons returning for treatment. The 

ability of some tests to detect C. trachomatis and N. gonorrhoeae 

in the same specimen might also affect the choice of test (see 

Methods To Enhance Performance or Reduce Costs). Recommendations for transporting and storing specimens must also 

be considered (Appendix D). 

Economic Analysis 

Economic analyses can assist in selecting the optimal tests 

and strategy for C. trachomatis and N. gonorrhoeae screening. 

Moreover, economic analyses can be relevant for STD screening because, in the absence of symptoms or signs, the cost of 

screening tests, including the costs of labor and other nonkit 

costs, is often not reimbursed by insurance plans or other payers. Thus, knowing the costs and benefits of a screening 

program that might not be fully reimbursed can be critical to 

decision makers (Box 4). 

Laboratory Environment 

The laboratory must consider how candidate tests match 

the laboratory environment. For example, laboratories must 

satisfy the requirements for physical space, separation of work 

areas (e.g., sample processing and amplification), and use of 

any special equipment (e.g., biosafety cabinets) as recommended by the test kit manufacturer. Differences in throughput among different NAATs must be considered. Additional 

considerations include technician time, turnaround time, technical difficulty, equipment costs, and time required to maintain equipment. Laboratories are encouraged to investigate 

these concerns and their impact on cost-effectiveness when 

choosing among the available testing methods. 

Need for Additional Testing To Support 

C. trachomatis or N. gonorrhoeae Diagnoses 

Efforts to maximize test sensitivity to avoid missing the 

opportunity to identify and treat infected persons might warrant tolerating a certain number of false-positive diagnoses. 

However, consideration must also be given to reducing 

the rate and consequences of false-positive tests. All tests, 

including culture for C. trachomatis, occasionally generate falsepositive results. For these reasons, all positive tests are considered to be presumptive evidence of infection (Box 5). 

Regardless of health-care provider setting, patient population, 

and patient characteristics, a false-positive test result for 

C. trachomatis or N. gonorrhoeae can have adverse medical, 

social, and psychological impacts for a patient. In such cases, 

consideration should be given to performing an additional 

test to verify a positive screening test. 

The potential for false-positive test results complicates the 

interpretation of positive tests among patients in populations 

with a low prevalence of infection. This occurs because 

the proportion of total positive tests that are truly positive 

(i.e., PPV) is lower among such a population. Consideration 

should be given to routine additional testing for persons with 

positive C. trachomatis or N. gonorrhoeae screening tests when 

risk-factor information or actual surveys indicate that the prevalence is low, resulting in a lower PPV (e.g., <90%) (see 

C. trachomatis and N. gonorrhoeae Test Performance When 

Used for Screening). 

Economic analysis of additional testing to increase the specificity of a screening test is problematic because the primary 

benefit of such additional testing is in averting costs that are 
Vol. 51 / RR-15 Recommendations and Reports 13 

Box 4. Performing an economic analysis 

The information in this box is not intended as a guide to When calculating costs and benefits of screening, programs 

conducting economic analyses, which is beyond the scope of should define the perspective of interest (e.g., a specific prothese guidelines. Resources are available that explain the theory vider or practice, the sexually transmitted disease [STD] proand process in detail.* The simplest economic analysis is a gram of a state health department, a commercial laboratory, a 

cost-analysis in which the costs of delivering a service or op- managed care organization, the entire health-care system, or 

erating a program are determined. Cost-effectiveness analy- society). The perspective determines which costs and bensis (CEA) estimates the cost of an intervention per unit efits are included in the calculations. For example, a societal 

outcome that the intervention generates (e.g., infections perspective CEA includes all costs and benefits associated with 

treated or cases of pelvic inflammatory disease [PID] avoided). a program, whereas a health-care–system perspective CEA inCEA is most useful for comparing different interventions that cludes direct medical costs but excludes costs borne solely by 

achieve the same outcomes.† patients (e.g., transportation and lost productivity). Published 

The terms cost-effective and cost-saving are commonly used CEAs usually use one of these two perspectives.¶ 

interchangeably, but they do not mean the same thing. For An interactive computer program named SOCRATES 

example, if a program is cost-saving, that means the cost of (Screening Optimally for Chlamydia: Resource Allocation, 

implementing a program is less than the health-care costs the Testing, and Evaluation Software) is now available at the CDC 

program prevents. A program is cost-effective if it uses resources website to aid in test selection and methods to reduce costs 

efficiently, compared with alternative uses for the same resources.§ for screening for C. trachomatis infection among asymptomatic women. SOCRATES is a simple cost-effectiveness model Calculating Screening Costs and Benefits that uses a broad health-care–system perspective to analyze Programs considering an economic analysis of their screen- the costs involved in using nucleic acid amplification, nucleic ing activities should consider direct medical costs, including acid hybridization, and enzyme immunoassay tests, singly or test kits, reagents, and specimen-collection materials. They with gray-zone testing, among patient populations with posi­ should also consider health-care providers’ time for collecting tivity rates that can be set and changed by the user. Costs of specimens, administration, overhead and facilities costs, and testing and treatment can also be set and changed by the user. specimen packing and transport. The testing facility must also This program is available at http://www.cdc.gov/nchstp/dstd/ consider costs incurred in changing test technology (i.e., startup HEDIS.htm. equipment, laboratory remodeling costs, or such recurring costs 

as training) and any changes in number or level of staff. Role of Economic Analysis 

To measure screening benefits, programs should consider Economic analysis should rarely be the driving force for 

the savings realized through averted medical costs (e.g., costs test selection and screening strategies, but it should be conassociated with cases of PID averted through detecting and sidered with other factors (e.g., test performance, ease of specitreating C. trachomatis and N. gonorrhoeae infections). Other men collection, laboratory capacity, population prevalence, 

health outcomes that might be of interest are epididymitis in and disease prevention goals of the screening program). Cermen, uncured infections in men that might lead to reinfec- tain testing approaches that are recommended in these guidetion of sex partners, and neonatal complications. Other lines (see Methods To Enhance Performance or Reduce Costs) 

averted costs include indirect costs (e.g., lost productivity are difficult to assess by using CEA, because such concerns as 

because of disease) or intangible costs (e.g., patient pain and the repercussions of delivering a false-positive test result to a 

suffering). However, the indirect and intangible costs of sexu- patient are difficult to value in monetary terms.

ally transmitted diseases are inadequately researched. 

* Sources: Haddix AC, Teutsch SM, Shaffer PA, Duñet DO. Prevention effectiveness: a guide to decision analysis and economic evaluation. New York, NY: Oxford 

University Press, 1996. Gold MR, Siegel JE, Russell LB, Weinstein MC. Cost-effectiveness in health and medicine. New York, NY: Oxford University Press, 1996. † Other common economic analyses include cost-utility and cost-benefit. Cost-utility analysis converts cost-effectiveness outcomes to quality-adjusted life years 

(QALYs) or disability-adjusted life years (DALYs). Cost-utility analyses are rare in sexually transmitted diseases (STD) because the QALY or DALY impacts of STD 

and their sequelae are unresearched. Cost-benefit analysis converts the outcomes achieved by a program to dollar values so that the effects of different programs (e.g., 

STD screening and environmental health) can be directly compared (Source: Haddix AC, Teutsch SM, Shaffer PA, Duñet DO. Prevention effectiveness: a guide to 

decision analysis and economic evaluation. New York, NY: Oxford University Press, 1996). 

§ For example, if a program incurs $1,000 for screening and treating women for C. trachomatis and, therefore, avoids $2,000 in treatment costs for PID, the program 

is cost-saving. However, the program might still be cost-effective even if the program does not avert enough sequelae costs to be cost-saving. A program that has a net 

cost (program costs minus averted sequelae costs) of $500/case of PID averted might be considered cost-effective, compared with the first program, although it is 

more expensive, if it prevented more cases. The determination of whether such a program is cost-effective requires that a judgement be made regarding the value of 

the health outcomes in question. No universally applicable rules exist. 

¶ The choice of perspective can influence the conclusions of a cost-effectiveness analysis. In the previous example, done from a health-care–system perspective, 

program costs were $1,000/woman, and averted PID costs were $2,000, making the program cost-saving. Certain PID costs (e.g., those for infertility treatments) 

routinely occur after the initial infection, and the program conducting the testing might never incur them. The program doing the testing might only reduce its costs 

for sequelae by $800 (for treatment of acute PID) for every $1,000 spent on screening. From the perspective of the individual program, screening might not be costsaving. A societal perspective provides the truest indication of the cost-effectiveness of a program, but a more limited perspective can point to the impact on a given 

provider or program, including the barriers to implementation of new tests or screening programs. 
14	 MMWR October 18, 2002 

BOX 5. Additional testing and patient management after a Methods To Enhance Performance positive screening test or Reduce Costs 

•	 All positive screening tests should be considered pre­ Different approaches have been used to increase the effisumptive evidence of infection. ciency of standard screening methods. Although selective 

•	 An additional test should be considered after a posi­ screening is not a laboratory method, using selective screentive screening test if a false-positive screening test would ing criteria is included in the following discussion because the 

result in substantial adverse medical, social, or predictive values and cost to detect an infection are strongly 

psychological impact for a patient. influenced by infection prevalence. Another approach is to 

•	 Consideration should be given to routinely perform­ use a NAAT to test specimens that yield results from an EIA 

ing an additional test after a positive screening test or unamplified nucleic acid probe test that fall in a zone around 

if the positive predictive value is considered low the cutoff (i.e., gray zone). This technique warrants further 

(e.g., <90%). evaluation as a method to decrease the gap in sensitivity 

•	 Patients should be counseled regarding prompt treat­ between NAATs and other tests without incurring the full 

ment after a positive screening test because an addi­ additional cost of testing all specimens with a NAAT. Interest 

tional test might be falsely negative. in pooling specimens for testing by a NAAT is similarly motivated. Augmenting screening tests with additional testing to 

improve test specificity is of increasing importance because intangible. These include psychosocial costs that can result C. trachomatis and N. gonorrhoeae prevalences have declined from a false-positive test result. These costs vary according to after the introduction of screening programs and because setting and are not well-researched. The benefits of reducing C. trachomatis screening has expanded into lower prevalence these intangible costs must be weighed against the tangible populations. Using test formats (e.g., nucleic acid probe tests direct costs of performing the confirmatory tests. Fortunately, or NAATs) that permit testing for both C. trachomatis and these costs apply only to patients who initially test positive N. gonorrhoeae might reduce costs. Finally, the urine leuko­ and frequently constitute only a limited proportion of total cyte esterase test, which has a low sensitivity but is inexpen­ costs per positive test, particularly in low prevalence settings sive, has been used to select specimens for testing with a specific where the additional testing is typically needed (see Methods C. trachomatis or N. gonorrhoeae test when use of a more To Enhance Performance or Reduce Costs). sensitive initial test was not feasible. 

Consideration of Point-of-Care Testing Selective Screening To Increase the Point-of-care tests for C. trachomatis screening are less sen­ Percentage of Positive Tests sitive than laboratory-based tests but should be considered in Selecting persons for testing who are at high risk can situations where screening-test–positive persons might fail to increase the prevalence of infection among tested persons, return for treatment or return after substantial delays. Point- thereby reducing screening costs to detect persons with of-care tests are not a cost-effective option if they are pro­ C. trachomatis infection. Symptoms or signs are not included cessed after the patient visit because they are relatively as screening criteria because they warrant immediate diagnos­ insensitive and require labor-intensive processing. Each health- tic testing. Evaluations of screening algorithms for care provider needs to compare the sensitivities, costs, and C. trachomatis, including an algorithm recommended by CDC treatment rates for point-of-care and laboratory-based tests. in 1993 (31), have been published (96–104). The third U.S. Providers need to determine whether the opportunity to pro­ Preventive Services Task Force (USPSTF) reviewed this infor­ vide treatment to certain patients who would otherwise go mation and published C. trachomatis screening recommenda­ untreated warrants the additional cost and less favorable sentions (105) (available at http://www.ahrq.gov/clinic/ sitivity of point-of-care testing. FDA-cleared C. trachomatis 

uspstfix.htm) (Appendix E). USPSTF also concluded that and N. gonorrhoeae tests that can be performed rapidly enough satisfactory urine screening tests for men had been introduced to qualify as point-of-care tests must be performed in a CLIA- too recently for sufficient evidence to have been developed to certified laboratory because they are classified under CLIA as 

moderate complexity tests ( make screening recommendations. Using criteria to select 24). women or men to screen for N. gonorrhoeae infection has 

received only limited evaluation, although the prevalence of 

N. gonorrhoeae is usually lower than the prevalence of 

C. trachomatis. Thus, concerns regarding the cost to detect an 
Vol. 51 / RR-15 Recommendations and Reports 15 

infection and PPV might be greater for N. gonorrhoeae than 

for C. trachomatis (106). 

Gray-Zone Testing To Improve Test 

Performance 

To establish the positive-negative cutoff value for a diagnostic test, a manufacturer attempts to achieve the highest 

sensitivity while keeping the specificity at or near 100%. This 

is done by setting the cutoff at the lowest level possible while 

minimizing false-positive results. Certain test readings from 

truly infected persons will fall below this cutoff value (falsenegatives). Often, a substantial proportion of the readings for 

persons with false-negative results cluster just below the cutoff, whereas the readings for persons with truly negative 

results are clustered farther below the cutoff. Consequently, a 

relatively narrow zone below the cutoff might exist within 

which the proportion of readings that are from truly infected 

persons is substantially higher than the proportion of readings 

farther below the cutoff. The ratio of true positives to true 

negatives in this zone is affected by the prevalence of infection 

as well as by test performance among the tested population. 

Similarly, false-positive results are clustered just above the cutoff, whereas the readings for persons with truly positive 

results are clustered farther above the cutoff. A relatively narrow zone above the cutoff might exist within which the proportion of readings that are from truly uninfected persons is 

substantially higher than the proportion of readings farther 

above the cutoff. When screening test results are in these zones, 

commonly called the negative and positive gray zones, respectively, a laboratory has the option of retesting specimens with 

another test. 

By using a NAAT to retest specimens with gray-zone results 

from less sensitive and less expensive screening tests, the sensitivity and specificity of the screening test might be improved 

at less cost than switching entirely to the NAAT. However, 

such a restricted use of a NAAT might be less sensitive than 

testing the entire population with a NAAT. A NAAT is also 

theoretically preferable to a competition or blocking antibody 

assay for additional testing of specimens from persons with 

positive non-NAAT screening tests (see Additional Testing To 

Improve Test Specificity). Testing strategies that combine use 

of a NAAT by itself in higher prevalence populations and as 

an additional test after gray-zone non-NAAT results among 

lower prevalence populations warrant further evaluation. Laboratories should establish feasibility, cost-effectiveness, and grayzone limits before implementation of the strategy. 

Although gray-zone testing with a NAAT has been evaluated in multiple studies (107–113), these studies have not 

employed independent reference standards. In certain cases, 

the second test was performed on the specimen that was tested 

by the screening test. If the second test has not been cleared by 

FDA for use with that type of specimen, CLIA requires that 

the laboratory conduct a study to establish the performance 

of the second test when conducted on the screening test specimen (Appendix C). This regulatory requirement is critical 

because NAATs might generate more false-positive and falsenegative results when performed on specimens collected 

for tests designed with less stringent protection against 

contamination and amplification enzyme inhibitors. Grayzone testing must be evaluated in appropriately designed 

research studies by using an independent reference standard 

before a recommendation is made regarding its utility in 

routine practice. 

Pooling Specimens To Reduce Costs 

Because of the high sensitivity of NAATs, pooling specimens before testing for C. trachomatis and N. gonorrhoeae with 

LCR and PCR has been proposed as a method of reducing 

costs (114–120). Samples of individual specimens are first 

combined into a pool, which is then tested by a NAAT. If the 

pool is negative, all specimens forming the pool are reported 

as negative. If the pool is positive, a second aliquot of each 

specimen that contributed to the pool is tested individually. 

The potential cost-savings with pooling increases with decreasing prevalence of infection, because more specimens can be 

included in a pool at lower prevalences without increasing the 

probability of a pool testing positive. Available evidence indicates that pooling might be a cost-effective alternative to testing individual specimens with minimal if any loss of sensitivity 

or specificity (114–120). However, insufficient data exist from 

published, peer-reviewed studies that address the implementation or performance concerns raised by pooling to make a 

recommendation concerning testing of pooled specimens. 

Theoretically, pooling could either increase or decrease the 

sensitivity and specificity of a NAAT compared with processing individual specimens. To be reported as positive, pooled 

specimens must be positive according to the pooled result and 

according to the individual test. This requirement should contribute an increase in specificity and a decrease in sensitivity 

compared with individual testing. In addition, pooling could 

reduce NAAT sensitivity because the majority of pooling protocols result in a reduced amount of an individual specimen 

being tested. Moreover, pooling can permit inhibitors present 

in a single specimen to cause specimens that would have been 

truly positive when tested individually to be falsely negative 

when tested in a pool. Such inhibition will go undetected if 

an internal control for inhibition is not included when testing 

pooled specimens. Conversely, dilution of specimens by pooling can decrease the effect of inhibitors. Pooling adds testing 

and data-recording steps that can result in errors and report­
16	 MMWR October 18, 2002 

ing of additional false-positive or false-negative results. In •	 the nucleic acid target, antigen, or phenotype (e.g., colisaddition, pooling results in a higher number of specimens in tin resistance, oxidase production) detected by the test is 

a run being positive. This increases the chances for sub­ possessed by organisms in the specimen other than 

optimal technique (e.g., by pipetting) to result in cross- C. trachomatis or N. gonorrhoeae; 

contamination and false-positive results. •	 the detection system generates a signal in the absence of 

Published studies of pooling using PCR and LCR tests for target; 

C. trachomatis and N. gonorrhoeae are still limited, and the •	 the specimen becomes contaminated; and 

majority of such studies have been conducted without • staff make data entry errors. 

an independent reference standard. Nevertheless, published Approaches to detect false-positive results by applying an 

studies indicate that pooling 4–10 urine or endocervical additional test can be ordered by preference on the basis of 

specimens before testing can substantially reduce costs and theoretical considerations (Box 6). 

improve throughput while maintaining the high performance Theoretically, testing a second specimen with a different type 

characteristics associated with NAATs (114–120). Savings from of test is least likely to confirm a false-positive result, whereas 

reduced reagent costs have ranged from 40% to 60%. repeating the original test on the original specimen is most 

Because of the increased complexity of the pooling protocol, likely to do so. Using a NAAT as an additional test after a 

savings in personnel time are proportionately less than the positive non-NAAT test might be an effective and highly ecosavings in reagent costs. nomical approach that deserves additional evaluation. HowIn addition to these performance concerns, the following ever, except when culture is used to obtain an isolate, a 

concerns should be addressed when considering use of pooling: non-NAAT should not be used as an additional test after a 

•	 what procedures to follow when all the individual speci­ NAAT because of the lower sensitivity of non-NAATs. Such 

mens from a positive pool provide negative results (e.g., additional testing could be extended to persons with nontest for inhibition); NAAT screening test results in the gray zone (see Gray-Zone 

•	 use of internal amplification controls to detect inhibition; Testing To Improve Test Performance). An advantage of iso­

•	 the need to inform the provider or patient that specimens lating the organism by culture is flexibility in the choice of 

are being tested by using a pooling protocol; multiple additional testing procedures, and compared with 

•	 how to report test results; and NAATs, a reduced risk of error caused by contamination dur­

• reimbursement by third-party payers. ing initial or subsequent testing. Using an FDA-cleared test as 

Because pooling is a modification of FDA-cleared procedures, an additional test to verify the positive results of a screening 

laboratories that implement pooling of patient specimens must test does not by itself introduce additional requirements 

satisfy CLIA requirements by establishing performance speci­ under CLIA (24). However, if the additional test is performed 

fications (Appendix C). on the original screening test specimen and the additional test 

has not been cleared by FDA for use with that type of specimen, Additional Testing To Improve Test Specificity CLIA requirements for establishing performance characteris­ An additional test might be indicated for a person with a tics (24) need to be satisfied (Appendix C). positive screening test result, if a false-positive result would Additional Testing After a Positive C. trachomatis Screenhave a serious adverse consequence (Box 5). Because treat­ ing Test. Selection of an additional test to verify a positive ments for C. trachomatis and N. gonorrhoeae are safe and rela­ C. trachomatis screening test is straightforward when a second tively inexpensive, the person might wish to receive and 

complete treatment while additional testing is being done, or BOX 6. Approaches to additional testing, in order by theoretical even if the additional test is negative. Routine additional test­ consideration, after a positive screening test 

ing to improve the predictive value of a positive screening test 

should be considered when the prevalence of either •	 Test a second specimen with a different test that uses a 

C. trachomatis or N. gonorrhoeae infection is low, resulting in a different target, antigen, or phenotype and a different 

low PPV (e.g., <90%) (see C. trachomatis and N. gonorrhoeae format. 

Test Performance When Used for Screening and also, Addi­ •	 Test the original specimen with a different test that 

tional Considerations in Selecting a Screening Test). uses a different target, antigen, or phenotype and a 

False-positive results might occur for multiple reasons, different format. 

including the following: •	 Repeat the original test on the original specimen with 

a blocking antibody or competitive probe. 

•	 Repeat the original test on the original specimen. 
Vol. 51 / RR-15	 Recommendations and Reports 17 

specimen can be collected, as when a patient returns for screen­ specimen for the additional test also presents logistical diffiing test results or when the need for additional testing can be culties and increases cost. Studies have not been conducted to 

anticipated when the screening specimen is collected (Box 7). compare application of such different approaches. 

Using culture with a C. trachomatis-specific anti-MOMP stain Because of the greater sensitivity of NAATs, a NAAT is the 

as the additional test has the advantage of high specificity and only recommended additional test to verify a result from 

flexibility in choice of additional testing, if warranted. How­ another NAAT and is, potentially, a superior additional test 

ever, culture lacks sensitivity and necessitates obtaining and to verify a non-NAAT positive C. trachomatis screening test. 

maintaining a suitable sample either at the initial or a subse­ Except for using culture to obtain an isolate, a non-NAAT 

quent visit. This fact has made culture less desirable. In addi­ should not be used as an additional test after a NAAT because 

tion, finding a laboratory to perform culture can be of the lower sensitivity of the non-NAAT. Using a NAAT as 

problematic. If obtaining a separate specimen for additional an additional test has received limited evaluation. In particular, 

testing is difficult, the additional test must perform adequately determining that NAAT specificity and sensitivity are not 

with the transport medium used for the screening test. reduced is critical if a NAAT is performed on specimens colUsing a blocking antibody format to verify a positive EIA lected, transported, and possibly processed by using nonscreening test and using a competitive probe format to verify NAAT procedures that might be less stringent with respect to 

a positive nucleic acid probe screening test have been the ad­ preventing contamination and inhibition of amplification 

ditional tests most widely used. The blocking antibody or com­ enzymes. 

petitive probe additional test is usually performed on the Manufacturers of NAATs for C. trachomatis infection have 

original screening specimen. These formats have been widely developed alternate target (e.g., MOMP targets) versions of 

used for additional testing, despite not being the theoretically their commercial tests that the manufacturers have employed 

preferred approaches. This is because approaches preferred on for resolving discrepant results in evaluation studies. Using 

theoretical grounds introduce the logistical and economic the same format for the additional test as for the screening test 

challenges of establishing a format for the additional test that offers logistical and economic advantages analogous to those 

differs from that of the screening test. Collecting a separate offered by the blocking antibody and competitive probe 

approaches for non-NAAT tests. Such assays are not offered 

commercially by NAAT manufacturers but might be in the future. BOX 7. Additional testing after a positive Chlamydia 

trachomatis screening test Additional Testing After a Positive N. gonorrhoeae Screening Test. Methods to confirm that Gram-negative, oxidase- Positive Nonnucleic Acid Amplification Tests positive, bacteria isolated on a selective culture medium are (Non-NAAT) N. gonorrhoeae have been reviewed (Box 8) (12,32). Acid 

•	 Culture with a C. trachomatis-specific anti-MOMP production from carbohydrates and the nucleic acid probe 

(major outer membrane protein) stain can be used culture confirmation test (AccuProbe,® manufactured by 

after a positive non-NAAT because of the high speci­ Gen-Probe, San Diego, California) are the most sensitive and ficity and the flexibility for additional testing, but cul­ specific methods. PACE 2 is also FDA-cleared for identifying ture poses increased difficulties in specimen transport N. gonorrhoeae. and storage. Pure growth on subculture is required for acid production 

•	 Competitive probe and blocking antibody formats can tests, but not for the AccuProbe test. AccuProbe is not known 

be used after positive nucleic acid probe tests and to cross-react with other organisms found in humans; enzyme immunoassays, respectively, but this approach however, variant strains of certain pathogenic and commensal is less likely, theoretically, to detect a false-positive Neisseria species can provide false-positive acid production result. results, and certain strains of N. gonorrhoeae might provide 

•	 A NAAT has high potential as an additional test after false-negative acid production results. Additional tests will be non-NAAT tests because of the increased sensitivity; required to differentiate between species that might produce however, this use of NAATs has received limited evaluation. acid from glucose but not from maltose, sucrose, or lactose 

(Appendix F) or to identify variant gonococcal isolates that Positive NAAT 

fail to produce acid from glucose. •	 Only another NAAT has a sufficiently high sensitivity Although nongonococcal pathogenic and commensal to serve as an additional test after a positive NAAT; Neisseria species are commonly found in the oropharynx, they however, such an approach to additional testing has are unusual in genitourinary specimens. Either the acid pro­ received limited evaluation. duction or the nucleic acid probe methods could be used for 
18	 MMWR October 18, 2002 

BOX 8. Additional testing after a positive Neisseria 

gonorrhoeae screening test 

Presumptively Positive Culture 

•	 Acid production from carbohydrates or the Gen-Probe 

AccuProbe® or PACE 2® tests are the preferred methods 

to confirm that typical, Gram-negative, oxidasepositive colonies are N. gonorrhoeae. 

•	 Requiring that both the acid production and nucleic 

acid probe methods be positive for N. gonorrhoeae ensures a high specificity. 

Positive Nonculture Test 

•	 Culture with confirmation as described previously is 

the preferred additional test after a positive nonculture 

test if specimen transport and storage conditions are 

suitable. 

•	 A competitive probe format might be used after a positive nucleic acid probe test, but this approach is less 

likely, theoretically, to detect a false-positive result. 

•	 A NAAT as an additional test after a nonculture test 

has received limited evaluation, and certain NAATs 

might cross-react with nongonococcal Neisseria 

species.* 

* Sources: Martin DH, Cammarata C, Van der Pol B, et al. Multicenter 

evaluation of AMPLICOR and automated COBAS AMPLICOR CT/NG 

tests for Neisseria gonorrhoeae. J Clin Microbiol 2000;38:3544–9. Van der Pol 

B, Martin DH, Schachter J, et al. Enhancing the specificity of the COBAS 

AMPLICOR CT/NG test for Neisseria gonorrhoeae by retesting specimens 

with equivocal results. J Clin Microbiol 2001;39:3092–8. Becton Dickinson. 

BDProbeTecTM ET Chlamydia trachomatis and Neisseria gonorrhoeae amplified 

DNA assays [Package insert]. Sparks, MD: Becton Dickinson, 1999. 

routine additional testing after presumptively positive screening cultures. Requiring that both types of tests be positive 

should guarantee an increased level of specificity. A detailed 

discussion of problems in differentiating N. gonorrhoeae from 

other Neisseria and related species is located at http:// 

www.cdc.gov/ncidod/dastlr/gcdir/NeIdent/Index.html. If an 

isolate cannot be conclusively identified as N. gonorrhoeae at a 

local laboratory, the isolate should be sent to a reference laboratory (e.g., a city, county, or state public health laboratory) 

for confirmation, chiefly in cases of alleged sexual assault or 

rape. 

Antibody tests (i.e., tests that detect gonococcal antigens) 

are not recommended for detection of N. gonorrhoeae. 

Coagglutination tests, which might cross-react with 

nongonococcal strains, are less sensitive or specific than acid 

production tests or the AccuProbe or PACE 2 tests. The 

monoclonal fluorescent antibody test for N. gonorrhoeae does 

not detect all gonococcal isolates and is not recommended as 

the primary test for detecting N. gonorrhoeae. 

Additional testing after positive nonculture screening tests 

for N. gonorrhoeae involves the same approaches that are 

described in the previous section for C. trachomatis. Because 

verification of positive nonculture tests for N. gonorrhoeae has 

received only limited evaluation and certain NAATs might 

cross-react with nongonococcal Neisseria species (54,56,57), 

substantial effort is warranted to arrange for culture and the 

assistance of a reference laboratory if a false-positive diagnosis 

of N. gonorrhoeae would have serious adverse consequences, 

as in testing of children. 

Reporting Test Results. When additional testing has been 

performed, the laboratory should report the results of both 

the screening test and the additional tests, as well as the overall interpretation. The laboratory has the responsibility to educate clinicians regarding the importance of all laboratory 

results, including both screening and additional test results. 

In particular, clinicians need to be aware of the limitations of 

the additional tests, including the possibility that they yield 

false-negative results when the screening test is positive. 

Because serious side effects from therapies for C. trachomatis 

and N. gonorrhoeae are uncommon, clinicians might recommend treatment after a positive screening test for a person at 

risk for infection, pending additional testing or even when a 

positive screening test is not verified by additional testing. 

Cotesting for C. trachomatis 

and N. gonorrhoeae To Reduce Costs 

Multiple tests permit testing for both organisms by using 

the same specimen. The prevalence of N. gonorrhoeae is less 

than C. trachomatis in the majority of areas of the United States; 

however, the prevalence of each varies widely, even within such 

limited areas as cities or counties. Usually, screening for 

N. gonorrhoeae will not be justified unless screening for 

C. trachomatis is also warranted. Decisions regarding screening for either or both organisms should not be made without 

a careful evaluation of the local epidemiology of N. gonorrhoeae 

and C. trachomatis. 

Cotesting for C. trachomatis and N. gonorrhoeae by using 

tests specially designed for such cotesting should be considered, if transport conditions would reduce the sensitivity of 

N. gonorrhoeae culture or if using such tests reduces the cost. 

However, provision should be made to perform an additional 

test to improve test specificity whenever indicated (see Additional Testing To Improve Test Specificity) and to obtain 

isolates for antimicrobial susceptibility testing in the case of a 

repeated treatment failure (see Test of Cure, Treatment Failure, and Antimicrobial Resistance). 
Vol. 51 / RR-15	 Recommendations and Reports 19 

Using LET to Select for C. trachomatis 

or N. gonorrhoeae Tests 

LET, which has a low sensitivity but is inexpensive, has been 

used to select specimens for testing with a specific C. trachomatis 

or N. gonorrhoeae test when universal testing with a more sensitive initial test is not feasible. Studies have demonstrated that 

using a positive LET to select patients for screening with a 

more sensitive and specific test can be cost-effective. Published 

studies have focused primarily on asymptomatic men and have 

reported that this approach is more cost-effective when 

the prevalence is low (89,91,121–124). One study (121) 

determined that the negative predictive value of LET among 

asymptomatic men aged >30 exceeded 98%, thereby providing support for no additional C. trachomatis testing among 

that population. Among men aged <30 years, whether a negative result is a valid basis on which to exclude that population 

from testing with more sensitive tests is uncertain. Because 

the test does not detect either C. trachomatis or N. gonorrhoeae, 

but rather nonspecific inflammatory enzymes, a positive LET 

should be followed by specific tests for C. trachomatis and 

N. gonorrhoeae. The importance of a positive LET that is followed by negative tests for C. trachomatis and N. gonorrhoeae 

is unknown, but could indicate infection with other organisms (e.g., Trichomonas vaginalis, Ureaplasma urealyticum, or 

Mycoplasma genitalium). 

Collecting, Transporting, and
 

Storing Specimens
 

Correct specimen collection and handling techniques are 

critical for all methods used to identify C. trachomatis and 

N. gonorrhoeae. Even diagnostic tests with the highest performance characteristics cannot produce accurate results when 

specimens submitted to the laboratory are incorrectly collected. 

Recommendations for transporting and storing specimens are 

summarized in this report (Appendix D). 

Clinicians require training and periodic assessment to maintain correct technique for specimen collection (125–127). The 

presence of columnar epithelial cells has been associated with 

increased sensitivity in the majority of studies that evaluated 

collection of endocervical specimens for C. trachomatis screening with NAATs as well as other types of tests (125–132). 

How these results apply to other types of specimens is 

unclear. Obtaining columnar cells is less critical for detecting 

N. gonorrhoeae than for detecting C. trachomatis. 

Collecting and Transporting Specimens 

for Screening 

Specimen Collection Recommendations 

Applicable to Culture and Nonculture Tests 

Although the requirement for columnar endocervical 

cells applies less to N. gonorrhoeae than to C. trachomatis, 

guidelines included in this report are appropriate for both 

organisms (Box 9). 

Specific Requirements for C. trachomatis 

Culture 

Swabs with plastic or wire shafts can be used to obtain specimens for cell culture (133–135). Swab tips can be made of 

cotton, rayon, or Dacron,® but should not be made of 

calcium alginate (133–136). Swabs with wooden shafts should 

not be used because the wood might contain substances that 

are toxic to C. trachomatis or tissue culture cells (133–135). 

As part of routine quality control, samples of each lot of swabs 

that are used to collect specimens for C. trachomatis isolation 

should be screened for possible inhibition of C. trachomatis 

growth and toxicity to tissue culture cells. 

The substitution of an endocervical brush for a swab might 

increase the sensitivity of culture for endocervical specimens 

from nonpregnant women (137). However, using an endocervical brush might induce bleeding. Although such bleeding 

does not interfere with the isolation of C. trachomatis, patients 

should be advised regarding possible spotting. 

When culture isolation of C. trachomatis from women is to 

be performed, processing a specimen from the urethra as well 

as the endocervix can increase sensitivity by 23% (138). Placing the two specimens in the same transport container is 

acceptable. The viability of C. trachomatis organisms must be 

maintained during transport to the laboratory (28). 

•	 When the elapsed time between specimen collection and 

inoculation is <24 hours, specimens should be stored at 

4o

C and inoculated in cell culture as quickly as possible. 

•	 When specimens cannot be inoculated in <24 hours, the 

specimens should be maintained at <–70o

C. 

• Specimens for culture should never be stored at –20o

C or 

in frost-free freezers. 

Specific Requirements for N. gonorrhoeae 

Culture 

Swabs with plastic or wire shafts can be used to obtain specimens for culture. Swab tips can be made of rayon, Dacron, or 

calcium alginate. Obtaining a second cervical specimen for 

N. gonorrhoeae culture is associated with an increase in sensitivity (139). Inoculating the two specimens on the same 

culture plate is acceptable. 
20	 MMWR October 18, 2002 

BOX 9. Specimen-collection guidelines 

Endocervical Specimens 

•	 Nonculture specimens should be obtained as directed 

by the test manufacturer in the package insert. 

•	 By established practice, specimens for C. trachomatis 

tests are obtained after specimens for Gram-stained 

smear or N. gonorrhoeae culture. When a Papanicolaou smear is to be collected, whether specimens for 

C. trachomatis or N. gonorrhoeae should be collected 

first or last is unknown. Bleeding can occur when a 

Papanicolaou smear is obtained first, and gross blood 

interferes with certain tests for C. trachomatis and 

N. gonorrhoeae. 

•	 Before obtaining a specimen, a sponge or large swab 

should be used to remove all secretions and discharge 

from the cervical os. 

•	 For nonculture tests, the swab supplied or specified 

by the test manufacturer should be used. 

•	 The appropriate swab or endocervical brush should 

be inserted 1–2 cm into the endocervical canal (i.e., 

past the squamocolumnar junction). The swab should 

be rotated against the wall of the endocervical canal 

>2 times or for the period of time recommended by 

the manufacturer. The swab should be withdrawn without touching any vaginal surfaces and placed in the 

appropriate transport medium. 

Urethral Specimens 

•	 Specimens should be obtained as directed by the test 

manufacturer in the package insert. 

•	 If possible, obtaining specimens should be delayed until 

>1 hour after the patient has voided. 

•	 Specimens should be obtained for C. trachomatis tests 

after obtaining specimens for a Gram-stained smear 

or N. gonorrhoeae culture. 

•	 For nonculture tests, the swab supplied or specified 

by the manufacturer should be used. 

•	 The urogenital swab should be inserted gently into 

the urethra (females, 1–2 cm; males, 2–4 cm). The 

swab should be rotated in one direction for >1 revolutions and withdrawn. For males or females with urethral discharge, exudate collected from the urethral 

meatus is sufficient for N. gonorrhoeae culture. An 

intraurethral specimen is required for C. trachomatis 

testing, regardless of the presence of exudate at the meatus. 

Urine Specimens 

•	 Specimens should be obtained as directed by the test 

manufacturer in the package insert. 

•	 If possible, specimen collection should be delayed until 

>1 hour after the patient has voided.* 

•	 First-catch urine (e.g., the first 10–30 cc voided after 

initiating the stream) should be used. 

* Source: Sellors J, Chernesky M, Pickard L, et al. Effect of time elapsed since 

previous voiding on the detection of Chlamydia trachomatis antigens in urine. 

Eur J Clin Microbiol Infect Dis 1993;12:285–9. 

The viability of N. gonorrhoeae organisms must be maintained during transport to the laboratory; therefore, the following recommendations are made for transporting specimens: 

•	 Specimens should be inoculated directly onto a selective 

or nonselective (if the specimen is from a sterile site) 

nutritive medium (e.g., Martin-Lewis or chocolate agar 

containing IsoVitaleX,® respectively). 

• Specimens should be incubated at 35o

C–36.5oC in a CO2­

enriched atmosphere immediately after collection. 

•	 For transport to a local laboratory, placement of the 

inoculated plates in a CO2-enriched atmosphere is more 

critical than incubation at 35o

C–36.5oC (140–142). 

Inoculated media can be held at room temperature in a 

CO2-enriched atmosphere for <5 hours without a loss of 

viability. 

•	 For transport to a remote laboratory, specimens should 

be inoculated onto commercial transport media (e.g., 

JEMBEC® or Transgrow media). Inoculated media should 

be incubated for 18–24 hours before being transported, 

and the specimen should arrive <48 hours after collection 

from the patient. Specimens should not be transported in 

Stuart’s, Amies’, or other such media; specimens are 

diluted and organisms might lose viability if delays in shipping occur. If specimens must be transported in extreme 

hot or cold conditions, the specimens should be placed in 

an insulated Styrofoam® container. Detailed directions 

for collection of specimens for culture of N. gonorrhoeae 

have been described elsewhere (12,143,144). 

Adequacy of Endocervical Specimens 

Without endocervical specimen quality assurance, >10% of 

specimens collected for C. trachomatis testing are probably 

unsatisfactory because they contain secretions or exudate, but 

lack endocervical cells (126,128,145). A substantially reduced 

likelihood exists of detecting C. trachomatis in inadequate specimens by all tests, including NAATs (125–132). 

Assessing Endocervical Specimen Quality. Health-care 

providers and laboratorians are encouraged to evaluate the effect on endocervical C. trachomatis test positivity rates of monitoring the endocervical columnar cell content of specimens 

and then providing feedback and, as indicated, training to 

clinicians. Until proven unnecessary, routine or periodic assessment of endocervical specimen quality is recommended 

for all types of C. trachomatis tests. A report presenting alternative methods of measuring specimen quality has been developed by the National Chlamydia Laboratory Committee 

for the CDC-supported C. trachomatis screening program and 

distributed to constituent screening programs (additional 

information is available at http://www.aphl.org/ 

chlamydia_lab.cfm). The majority of published studies have 
Vol. 51 / RR-15	 Recommendations and Reports 21 

categorized specimens dichotomously as either containing the 

appropriate endocervical cells or not. In one study, a doseresponse association between quantity of the appropriate 

endocervical cells and the C. trachomatis positivity rate was 

demonstrated by using a multiple-category scale for quantity 

of appropriate cells (132). This study also prescribed a systematic process for reviewing slides. Diff-Quick stain has been 

described as efficient and inexpensive (125). 

The principal purpose of assessing the quality of endocervical specimens is to determine whether the sensitivity of 

C. trachomatis tests would be enhanced by providing feedback 

and training to clinicians. No evaluations have been published 

of the cost-effectiveness of alternative approaches to measuring the quality of endocervical cell specimens and improving 

specimen-collection practices, and no studies have correlated 

measures of specimen adequacy with test positivity for specimens collected for N. gonorrhoeae testing. 

Reporting and Follow-Up of Inadequate Specimens. An 

inadequate specimen should be reported as inadequate. Whenever possible, a second specimen should be collected for 

repeat testing. 

Collecting Specimens for Indications 

Other Than Screening 

Anatomic site-specific recommendations for application of 

C. trachomatis and N. gonorrhoeae tests, including for medicolegal applications, are summarized in this report (Appendices 

A and B). Multiple sources provide directions for collecting 

specimens for N. gonorrhoeae testing (12,143,144). 

Laboratory Implementation 

of NAATS 

NAATs require more attention to procedural details and 

development and maintenance of quality control systems than 

other nonculture screening tests (e.g., EIAs and nonamplified 

nucleic acid hybridization assays). An increase in such requirements results from the susceptibility of NAAT amplification 

enzymes to inhibition and the potential of NAATs to generate 

cross-contaminating target and to detect limited quantities of 

target present as a contaminant. Despite close attention to 

quality control, concerns regarding consistency of test performance and reproducibility persist, as indicated by reports of 

heterogeneity of results in clinical trials (78,80) and varying 

rates of reproducing positive results (146–151). 

As laboratories and health-care providers transition to 

amplification tests, certain critical concerns should be 

addressed, including 

•	 clinician training whenever a change occurs in the testing 

method. Training should address 

— indications for test use (e.g., appropriate types of specimens); 

— general instruction in obtaining adequate specimens 

from any site and specific instruction in obtaining a 

proper endocervical specimen (i.e., one that contains 

endocervical cells rather than ectocervical cells or vaginal material); 

— requirements for storage and transport; and 

— interpretation of test results. 

•	 monitoring of specimen collection and transport and 

periodic reinforcement of staff training. 

•	 development of standard laboratory operating procedures 

and quality-assurance protocols based on package inserts 

and any supplementary manufacturer instructions. 

Procedures and protocols should address 

— adoption of prescribed work areas and specimen handling procedures to avoid cross-contamination, which 

is of heightened importance because of the inherent 

sensitivity of amplification tests; 

— use of positive and negative controls, including a positive control from culture stock or known positive clinical specimens in addition to the control provided in 

the commercial kit; 

— trade-offs of using amplification controls to identify 

inhibitors (e.g., reducing false-negative results but decreasing throughput); and 

— creation of a data system that alerts laboratorians when 

a run includes an unusual number of positive specimens or when positive specimens are clustered within 

a run. 

•	 manufacturer-based training of laboratory staff with 

periodic retraining. 

•	 CLIA requirements for verifying or establishing test performance characteristics. If a laboratory is adopting an 

FDA-cleared test that is classified under CLIA as a highcomplexity test, CLIA requires conducting a study to verify 

that the test performs according to the manufacturer’s 

package insert claims (24). If the laboratory is adopting a 

test that has not been cleared by FDA or is adopting a 

modification of an FDA-cleared test, CLIA requires a more 

extensive study to establish performance specifications, 

because FDA-cleared package insert specifications are lacking (24) (Appendix C). 

•	 participation in a proficiency testing program. 
22 MMWR October 18, 2002 

Test of Cure, Treatment Failure, 

and Antimicrobial Resistance 

Test-of-cure is not recommended as a routine procedure 

after therapy for C. trachomatis or N. gonorrhoeae infection 

with first-line CDC-recommended treatment regimens, 

except after C. trachomatis therapy during pregnancy (152). 

Nonculture tests that are performed <3 weeks after completion of antimicrobial therapy might be falsely positive because 

of the presence of nonviable organisms; this applies in 

particular to NAATs (153–160). 

CDC recommends that clinicians contact their local or state 

health department for guidance and to arrange for antimicrobial susceptibility testing of isolates from patients apparently 

failing CDC-recommended therapy for C. trachomatis infection or CDC-recommended or FDA-approved therapy for 

N. gonorrhoeae infection. For this purpose, a patient’s infection is considered to have failed therapy if the patient is 

laboratory-test–positive for C. trachomatis or N. gonorrhoeae 

after treatment and the patient provides a history of having 

complied with the prescribed therapy and denies posttreatment sexual exposure to an untreated or new sex partner. 

Because knowledge is limited regarding the ability of 

C. trachomatis to develop antimicrobial resistance, CDC 

encourages health departments to inform CDC of treatment 

failures and, if possible, arrange for shipment of a swab specimen suitable for tissue culture for test confirmation. To 

report apparent C. trachomatis treatment failure, contact the 

following: 

Surveillance and Special Studies Section, Mail Stop E-02 

Epidemiology and Surveillance Branch 

Division of STD Prevention 

Centers for Disease Control and Prevention 

1600 Clifton Rd., N.E. 

Atlanta, GA 30333 

Phone: 404-639-8371 

Attention: Susan Wang, M.D. 

or Hillard Weinstock, M.D. 

To submit specimens for C. trachomatis testing, contact the 

following: 

Chlamydia Laboratory 

Syphilis and Chlamydia Branch, Mail Stop D-13 

Centers for Disease Control and Prevention 

1600 Clifton Rd., NE 

Atlanta, GA 30333 

Phone: 404-639-3785 

Attention: John Papp, Ph.D. 

CDC encourages health departments to inform CDC of 

N. gonorrhoeae treatment failures and, if possible, arrange for 

N. gonorrhoeae culture and testing of any isolate for susceptibility to CDC-recommended regimens used to treat patients. 

If susceptibility testing cannot be performed at a local or state 

laboratory, isolates should be submitted to CDC as should 

any isolate that is resistant to a CDC-recommended therapy. 

Antimicrobial susceptibility testing should be performed according to recommendations of the National Committee for 

Clinical Laboratory Standards (NCCLS), and results should 

be interpreted according to criteria designated by NCCLS. If 

NCCLS has not provided criteria for resistance for a CDCrecommended therapy (e.g., cephalosporins), an isolate is considered to be resistant if the isolate fails to meet the NCCLS 

criteria for susceptibility. NCCLS might not have designated 

criteria for definition of a susceptible category for antimicrobial agents that are used for gonorrhea treatment. When no 

NCCLS criterion is available, consult http://www.cdc.gov/ 

ncidod/dastlr/gcdir/Resist/diskdif.html for additional information or contact the Neisseria Reference Laboratory for further guidance. To report apparent N. gonorrhoeae treatment 

failure, contact the following: 

Surveillance and Special Studies Section, Mail Stop E-02 

Epidemiology and Surveillance Branch 

Division of STD Prevention 

Centers for Disease Control and Prevention 

1600 Clifton Rd., N.E. 

Atlanta, GA 30333 

Phone: 404-639-8371 

Attention: Susan Wang, M.D. 

or Hillard Weinstock, M.D. 

To submit specimens for N. gonorrhoeae testing, contact the 

following: 

Neisseria Reference Laboratory, Unit 31 

Gonorrhea Research Branch, Mail Stop C-13 

Bldg. 1 South/Room B260 

Centers for Disease Control and Prevention 

1600 Clifton Rd., N.E. 

Atlanta, GA 30333 

Attention: David Trees, Ph.D., 404-639-2134 

or Joan S. Knapp, Ph.D., 404-639-3470 

In addition, statewide programs should be maintained to routinely isolate gonococcal strains and monitor antimicrobial 

susceptibilities to CDC-recommended therapies and to other 

FDA-cleared therapies with established usage in the state. 

Sexual Assault and Sexual Abuse 

Detailed information concerning evaluation and treatment 

of suspected victims of sexual assault or abuse can be obtained 

from the 2002 STD treatment guidelines (152). Presented here 

are general guidelines pertaining only to C. trachomatis and 

N. gonorrhoeae infections (Box 10). Examination of victims is 
Vol. 51 / RR-15	 Recommendations and Reports 23 

BOX 10. General guidelines for testing specimens related to 

possible sexual assault or abuse 

•	 Endocervical specimens are appropriate for diagnosing C. trachomatis and N. gonorrhoeae infection of sexually active females. However, the immature vaginal 

epithelium of prepubescent females might be infected, 

and specimens can be taken from the vagina of these 

patients. 

•	 Culture is the recommended method for detecting 

C. trachomatis in urogenital, pharyngeal, and rectal 

specimens. 

— Only cell culture using standard methods that 

employ C. trachomatis-specific antibodies to detect intracytoplasmic inclusions should be used. 

— Nonculture/nonamplification tests for C. trachomatis 

are not sufficiently sensitive and specific for them 

to be used among either victims or alleged assailants implicated in a sexual assault. 

— Data, experience, and court cases are insufficient to 

assess the applicability of NAATs to detect 

C. trachomatis or N. gonorrhoeae in investigating 

sexual assault and abuse. However, certain researchers have indicated that NAATs for C. trachomatis 

could be used as an alternative to cell culture if cell 

culture is unavailable and if another NAAT that targets a different sequence can be performed as an 

additional test if the initial NAAT test is positive. 

•	 Culture is the recommended method for detecting 

N. gonorrhoeae in urogenital, pharyngeal, or rectal swab 

specimens. 

— Gram-negative diplococci isolated on gonococcal 

selective medium from vaginal, pharyngeal, or rectal specimens must be identified by the methods 

described previously (see Additional Testing After 

a Positive N. gonorrhoeae Screening Test) to 

obtain a confirmed identification. 

— Nonculture tests for N. gonorrhoeae are not sufficiently sensitive and specific for them to be used 

among either victims or alleged assailants implicated in sexual assaults. 

— Gram-stained smear of swab specimens should not 

be used to detect N. gonorrhoeae among victims of 

sexual assault or abuse. 

•	 All specimens and isolates from both suspected victims and alleged assailants should be stored at <–70o

C 

in the event additional testing is needed. 

required for two purposes: 1) to determine if an infection is 

present so that it can be successfully treated and 2) to acquire 

evidence for potential use in a legal investigation. 

Testing to satisfy the first purpose requires a method that is 

highly sensitive, whereas satisfying the second purpose requires 

a method that is highly specific. Because of the health and 

legal implications of test results, the additional time, labor, 

and cost of performing tests that are sensitive and highly specific are justified. Using highly specific tests is critical with 

preadolescent children for whom the diagnosis of a sexually 

transmitted infection might lead to initiation of an investigation for child abuse. Local legal requirements and guidance 

should be sought for maintaining and documenting a chain 

of custody for specimens and results that might be used in a 

legal investigation. 

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Vol. 51 / RR-15 Recommendations and Reports 25 

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28	 MMWR October 18, 2002 

Appendix A 

Indications for Chlamydia trachomatis Testing 

and Test Selection by Specimen Type 

Readers are cautioned to refer to the manufacturers’ test kit inserts for specific details. Information in this appendix represents 

general conditions for comparative purposes. 

Endocervical swabs/urethral swabs from males 

Indications 

•	 Screening 

— Females: When pelvic examination is indicated 

— Males: Urine might be more acceptable to asymptomatic males 

•	 Endocervicitis 

•	 Urethritis (males) 

•	 Diseases at other anatomic locations possibly caused 

by sexually acquired C. trachomatis infection 

— Pelvic inflammatory disease 

— Urethral syndrome 

— Bartholinitis 

— Epididymitis 

— Perihepatitis (Fitz-Hugh-Curtis syndrome) 

(females) 

— Proctitis 

— Reactive arthritis/Reiter syndrome 

— Conjunctivitis 

•	 Not recommended for prepubertal children 

Test selection 

•	 Nucleic acid amplification tests (NAATs) 

— Preferred because of high sensitivity relative to other tests 

•	 Nonculture/non-NAAT 

— Recommended when a NAAT is not available or not economical 

•	 Culture 

— Preferred when an isolate is needed (e.g., sexual abuse or treatment failure) 

•	 Point-of-care tests 

— Recommended only when the patient is likely to be lost to follow-up 

and when the test will be performed while the patient waits for results 

and possible treatment 

•	 Additional testing is recommended after an initial positive screening test if 

a low positive predictive value can be expected or if a false-positive result 

would have serious psychosocial or legal consequences 

Urethral swabs from females 

Indication	 

•	 Used with endocervical swab to increase sensitivity 

of culture for screening 

•	 Urethral syndrome 

Test selection 

• Culture 

— Increases sensitivity of culture of endocervical swab for screening by 

<23%* 

— Among C. trachomatis-infected persons, dysuria is associated with a † high frequency of a positive urethral culture

•	 Nonculture tests are not recommended 

Urine 

Indication Test selection 

• Females: Screening or testing 

• Males: Screening 

• NAAT 

— Recommended on the basis of increased sensitivity and ease of use 

— For males, sensitivity with urine has been lower than with urethral 

swab in the majority of studies,§ but not all¶ 

— Other tests are not recommended because of low sensitivity and, in the 

case of enzyme immunoassay (EIA) and lipopolysaccharide (LPS)-specific direct fluorescent antibody (DFA) tests, lower specificity 

— Additional testing is recommended after an initial positive screening 

test if a low positive predictive value can be expected or if 

a false-positive result would have serious psychosocial or legal 

consequences 
Vol. 51 / RR-15	 Recommendations and Reports 29 

Vaginal swabs, postmenarcheal adolescents and adults 

Indication Test selection 

•	 Screening/testing of women when pelvic examina­ •	 No test is recommended for use with vaginal swab specimens 

tion is not otherwise indicated — The Food and Drug Administration (FDA) has not cleared any 

nonculture test for use with vaginal specimens 

— NAAT 

Additional review is needed before a recommendation can be made; 

however, in multiple studies, sensitivity and specificity with a provideror client-collected vaginal swab has been similar to screening with endocervical or urine specimens 

Additional testing is recommended after an initial positive screening 

test if a low positive predictive value can be expected or if a positive 

result would have serious psychosocial or legal consequences 

— Culture 

Not recommended for adults because of suboptimal sensitivity 

— Other tests are not recommended because of low sensitivity and, in 

case of EIA and LPS-specific DFA, low specificity 

Vaginal swabs, prepubescent females 

Indication Test selection 

•	 Possible sexual abuse, children • Culture 

— Preferred for possibly sexually abused children because of presence of 

vaginal epithelium that is susceptible to C. trachomatis infection, high 

specificity, and ability to retain isolate for additional testing 

•	 FDA has not cleared any nonculture test for use with vaginal specimens 

•	 NAAT 

— When culture is not available, certain C. trachomatis specialists support 

using a NAAT if a positive result can be verified by another NAAT 

•	 Other tests are not recommended because of low sensitivity and, in the 

case of EIA and LPS-specific DFA, low specificity 

Rectal swabs 

Indication Test selection 

• Patients with history of receptive anal intercourse 

• Proctitis 

• Possible sexual abuse, children 

• Culture 

— Preferred when an isolate is needed (e.g., sexual abuse) 

— Sensitivity not well-defined; high specificity, especially if C. trachomatisspecific stain is used 

• DFA 

— FDA-cleared for use with rectal specimens 

— Limited evaluation in published studies 

— Sensitivity not well-defined; potentially high specificity if C. trachomatisspecific stain is used 

• Other tests are not recommended 

— NAAT 

Although cross-reactivity with other rectal bacteria has not been reported for NAATs, they have received only limited evaluation in published studies 
30 MMWR October 18, 2002 

Pharyngeal swabs 

Indication Test selection 

• Patients concerned regarding exposure during fellatio 

or cunnilingus 

• Newborns or infants (nasopharyngeal specimens) 

— Neonatal conjunctivitis 

— Pneumonia consistent with C. trachomatis 

etiology 

• Possible sexual abuse, children 

• Culture 

— Preferred method 

— Necessary when an isolate is needed (e.g., sexual abuse) 

— Sensitivity not well-defined; high specificity, including if 

C. trachomatis-specific stain is used 

• DFA 

— FDA-cleared for use with pharyngeal specimens 

— Limited evaluation in published studies 

— Sensitivity not well-defined; potentially high specificity if 

C. trachomatis-specific stain is used 

• Other tests are not recommended 

— NAAT 

Although cross-reactivity with other pharyngeal bacteria has not been 

reported for NAATs, they have received only limited evaluation in published studies** 

Conjunctival swabs 

Indication 

• Conjunctivitis among adults 

• Newborns or infants 

— Neonatal conjunctivitis 

— Pneumonia consistent with C. trachomatis etiology 

Test selection 

• Culture 

— Preferred, when available, because of high sensitivity and specificity 

• EIA, nucleic acid probe, and DFA tests 

— EIA, nucleic acid probe, and DFA tests that are FDA-cleared for use 

with conjunctival specimens have had uniformly high sensitivities with 

conjunctival specimens from newborns;†† evaluation studies are more 

limited for conjunctival specimens from adults with conjunctivitis 

— Specificities of tests on conjunctival specimens have also been high,†† 

although the potential for cross-reaction with other bacteria exists for 

EIA and for culture and DFA if used with stains that are not specific for 

C. trachomatis 

• Other tests are not recommended 

* Source: Jones RB, Katz BP, Van der Pol B, Caine VA, Batteiger BE, Newhall WJ. Effect of blind passage and multiple sampling on recovery of Chlamydia trachomatis 

from urogenital specimens. J Clin Microbiol 1986;24:1029–33. 

† Source: Paavonen J. Chlamydia trachomatis-induced urethritis in female partners of men with nongonococcal urethritis. Sex Transm Dis 1979;6:69–71. 

§ Sources: Stary A, Schuh E, Kerschbaumer M, Gotz B, Lee H. Performance of transcription-mediated amplification and ligase chain reaction assays for detection of 

chlamydial infection in urogenital samples obtained by invasive and noninvasive methods. J Clin Microbiol 1998;36:2666–70. Crotchfelt KA, Welsh LE, DeBonville 

D, Rosenstraus M, Quinn TC. Detection of Neisseria gonorrhoeae and Chlamydia trachomatis in genitourinary specimens from men and women by a coamplification 

PCR assay. J Clin Microbiol 1997;35:1536–40. Buimer M, van Doornum GJJ, Ching S, et al. Detection of Chlamydia trachomatis and Neisseria gonorrhoeae by ligase 

chain reaction-based assays with clinical specimens from various sites: implications for diagnostic testing and screening. J Clin Microbiol 1996;34:2395–2400. 

Carroll KC, Aldeen WE, Morrison M, Anderson R, Lee D, Mottice S. Evaluation of the Abbott LCx Ligase Chain Reaction Assay for detection of Chlamydia 

trachomatis and Neisseria gonorrhoeae in urine and genital swab specimens from a sexually transmitted disease clinic population. J Clin Microbiol 1998;36:1630–3. 

Ferrero DV, Meyers HN, Schultz DE, Willis SA. Performance of the Gen-Probe AMPLIFIED Chlamydia Trachomatis Assay in detecting Chlamydia trachomatis in 

endocervical and urine specimens from women and urethral and urine specimens from men attending sexually transmitted disease and family planning clinics. J Clin 

Microbiol 1998;36:3230–3. Ossewaarde JM, van Doornum GJJ, Buimer M, Choueiri B, Stary A. Differences in the sensitivity of the Amplicor Chlamydia trachomatis 

PCR assay. Genitourin Med 1997;73:207–11. Puolakkainen M, Hiltunen-Back E, Reunala T, et al. Comparison of performances of two commercially available 

tests, a PCR assay and a ligase chain reaction test, in detection of urogenital Chlamydia trachomatis infection. J Clin Microbiol 1998;36:1489–93. Stary A, Choueiri 

B, Hörting-Müller I, Halisch P, Teodorowicz L. Detection of Chlamydia trachomatis in urethral and urine samples from symptomatic and asymptomatic male 

patients by the polymerase chain reaction. Eur J Clin Microbiol Infect Dis 1996;15:465–71. 

¶ Sources: Van der Pol B, Quinn TC, Gaydos CA, et al. Multicenter evaluation of the AMPLICOR and automated COBAS AMPLICOR CT/NG tests for detection 

of Chlamydia trachomatis. J Clin Microbiol 2000;38:1105–12. Toye B, Peeling RW, Jessamine P, Claman P, Gemmill I. Diagnosis of Chlamydia trachomatis infections 

in asymptomatic men and women by PCR assay. J Clin Microbiol 1996;34:1396–1400. Vincelette J, Schirm J, Bogard M, et al. Multicenter evaluation of the fully 

automated COBAS AMPLICOR PCR test for detection of Chlamydia trachomatis in urogenital specimens. J Clin Microbiol 1999;37:74–80. Wiesenfeld HC, 

Uhrin M, Dixon BW, Sweet RL. Diagnosis of male Chlamydia trachomatis urethritis by polymerase chain reaction. Sex Transm Dis 1994;21:268–71. Young H, 

Moyes A, Horn K, Scott GR, Patrizio C, Sutherland S. PCR testing of genital and urine specimens compared with culture for the diagnosis of chlamydial infection 

in men and women. Int J STD AIDS 1998;9:661–5. 

**Source: Hammerschlag MR, Roblin PM, Gelling M, Tsumura N, Jule JE, Kutlin A. Use of polymerase chain reaction for the detection of Chlamydia trachomatis in 

ocular and nasopharyngeal specimens from infants with conjunctivitis. Pediatr Infect Dis J 1997;16:293–7. 

††Sources: Hammerschlag MR. Diagnosis of chlamydial infection in the pediatric population. Immunol Invest 1997;26:151–6. Hammerschlag MR. Chlamydia 

trachomatis in children. Pediatr Ann 1994;23:349–53. Hammerschlag MR, Roblin PM, Gelling M, Worku M. Comparison of two enzyme immunoassays to culture 

for the diagnosis of chlamydial conjunctivitis and respiratory infections in infants. J Clin Microbiol 1990;28:1725–7. Hammerschlag MR, Roblin PM, Cummings 

C, Williams TH, Worku M, Howard LV. Comparison of enzyme immunoassay and culture for diagnosis of chlamydial conjunctivitis and respiratory infections in 

infants. J Clin Microbiol 1987;25:2306–8. 
Vol. 51 / RR-15	 Recommendations and Reports 31 

Appendix B 

Indications for Neisseria gonorrhoeae Testing 

and Test Selection by Specimen Type 

Readers are cautioned to refer to the manufacturers’ test kit inserts for specific details. Information in this appendix represents 

general conditions for comparative purposes. 

Endocervical swabs/urethral swabs from males 

Indication 

•	 Screening 

— Females: When pelvic examination is indicated 

— Males: Urine might be more acceptable to asymptomatic males 

•	 Endocervicitis 

•	 Urethritis (males) 

•	 Diseases at other anatomic locations possibly caused 

by sexually acquired N. gonorrhoeae infection 

— Pelvic inflammatory disease 

— Urethral syndrome 

— Bartholinitis 

— Epididymitis 

— Perihepatitis (Fitz-Hugh-Curtis syndrome) 

(females) 

— Proctitis 

— Disseminated gonococcal infections 

— Conjunctivitis 

•	 Not recommended for prepubertal children 

Test selection 

•	 Gram-stained smear as a point-of-care test for males with urethral discharge 

— For males with urethral discharge, the sensitivity and specificity are 

similar to culture with oxidase testing and Gram-staining of any colonies with N. gonorrhoeae morphology 

— Culture after a positive Gram-stained smear might be useful for quality 

assurance, but additional testing is not usually otherwise indicated 

•	 Culture 

— Preferred if ambient conditions during holding and transport of inoculated media are adequate to maintain the viability of organisms 

Sensitivity and specificity of culture with additional testing 

approaches or surpasses that of other tests 

A culture isolate should be tested for antimicrobial resistance if a patient fails therapy 

Culture allows monitoring for antimicrobial resistance 

•	 Nucleic acid amplification tests (NAATs) or nucleic acid hybridization tests 

— Recommended when conditions during holding and transport of inoculated culture media are not adequate to maintain the viability of 

organisms 

— Commercial polymerase chain reaction (PCR)* and strand displacement assays† have cross-reacted with nongonococcal Neisseria; such 

cross-reactivity has not been reported for commercial ligase chain reaction (LCR) and unamplified probe assays 

•	 Additional testing is recommended after an initial positive screening test if 

a low positive predictive value can be expected or if a false-positive result 

would have serious psychosocial or legal consequences 

Urine 

Indication Test selection 

• Males: Screening 

• Females: Screening when pelvic examination is not 

indicated 

• NAATs 

— Sensitivity with urine might be lower than with urethral (males) or 

endocervical swabs§ 

— Other tests are not recommended because of low sensitivity 

— Additional testing is recommended after an initial positive screening 

test if a low positive predictive value can be expected because of a low 

prevalence or if a false-positive result would have serious psychosocial 

or legal consequences for a person 
32	 MMWR October 18, 2002 

Vaginal swabs, postmenarcheal adolescents and adults 

Indication 

•	 Screening/testing of women when pelvic examination is not otherwise indicated 

Test selection 

•	 No test is recommended for use with vaginal swab specimens. 

— The Food and Drug Administration (FDA) has not cleared any 

nonculture test for use with vaginal specimens 

— NAAT 

Additional review is needed before a recommendation can be made; 

however, in one study,¶ sensitivity and specificity with a provider- or 

client-collected vaginal swab was similar to screening with endocervical or urine specimens 

Additional testing is recommended after an initial positive screening 

test if a low positive predictive value can be expected or if a false-positive result would have serious psychosocial or legal consequences 

— Culture 

Not recommended for adults because of suboptimal sensitivity 

— Other tests are not recommended because of low sensitivity 

Vaginal swabs, prepubescent children 

Indication Test selection 

• Possible sexual abuse, children • Culture 

— Preferred for possibly sexually abused children because of presence of 

vaginal epithelium that is susceptible to N. gonorrhoeae infection, high 

specificity, and ability to retain isolate for additional testing 

• FDA has not cleared any nonculture test for use with vaginal specimens 

• NAATs 

— When culture is not available, certain specialists support use of a NAAT 

if a positive result can be verified by another NAAT 

• Other tests are not recommended because of low sensitivity and specificity 

Rectal swabs 

Indication	 Test selection 

•	 Patients with history of receptive anal intercourse • Culture 

•	 Proctitis — Preferred 

•	 Possible sexual abuse, children The sensitivity of culture is not well-defined; isolates that are oxidasepositive and Gram-negative diplococci should receive additional testing to verify an initial presumptive N. gonorrhoeae diagnosis, if a 

false-positive result would have serious medical, psychosocial, or legal 

consequences 

A culture isolate should be tested for antimicrobial resistance if a patient fails therapy 

•	 Other tests are not recommended 

Pharyngeal swabs 

Indication Test selection 

• Patients concerned regarding exposure during fella­ • Culture 

tio or cunnilingus — Preferred 

• Newborn or infant (nasopharyngeal specimens) Sensitivity of culture for pharyngeal specimens is not well-defined 

— Neonatal conjunctivitis Isolates that are oxidase-positive and contain Gram-negative diplococci 

• Possible sexual abuse, children should receive additional testing to verify an initial presumptive N. 

gonorrhoeae diagnosis because of the common occurrence of 

nongonococcal Neisseria in the pharynx 

A culture isolate should be tested for antimicrobial resistance if a patient fails therapy 

• Other tests are not recommended 
Vol. 51 / RR-15	 Recommendations and Reports 33 

Conjunctival swabs 

Indication	 Test selection 

•	 Conjunctivitis among adults • Gram stain as point-of-care test 

•	 Newborn or infant — Recommended to establish a presumptive diagnosis of 

— Neonatal conjunctivitis	 N. gonorrhoeae during a patient’s visit for conjunctivitis 

— Adequate sensitivity because of high concentration of organisms 

— Gram stain should be followed by laboratory-based testing 

because Gram-negative diplococci other than N. gonorrhoeae are occasionally isolated from conjunctiva 

•	 Culture 

— Preferred 

High sensitivity because of high concentration of organisms 

Oxidase-positive and Gram-stain–positive bacteria other than 

N. gonorrhoeae occasionally isolated from conjunctiva 

Inoculation onto nonselective media might increase sensitivity 

•	 Only a limited number, if any, nonculture tests are FDA-cleared for conjunctival specimens 

Diagnosing disseminated gonococcal infection, adults or neonates 

—	 Test selection 

• Gram stain as point-of-care test 

— Recommended on any synovial fluid and cerebrospinal fluid 

collected for other tests and on endocervical and urethral swab specimens 

— Gram stain should be followed by laboratory-based testing, which is 

more sensitive and specific 

•	 Culture 

— Preferred 

— Blood, synovial fluid from affected joints, and, if indicated, cerebrospinal fluid specimens should be inoculated onto nonselective as well as 

selective media 

— Swab specimens from the endocervix (adult female), vagina 

(neonate), urethra (adult male), rectum, and pharynx should be inoculated onto selective media 

— Additional testing recommended after an initial positive test to verify 

diagnosis 

• No other tests are recommended 

* Source: Martin DH, Cammarata C, Van der Pol B, et al. Multicenter evaluation of AMPLICOR and automated COBAS AMPLICOR CT/NG tests for Neisseria 

gonorrhoeae. J Clin Microbiol 2000;38:3544–9. 

†	 Source: Becton Dickinson. BDProbeTecTM ET Chlamydia trachomatis and Neisseria gonorrhoeae amplified DNA assays [Package insert]. Sparks, MD: Becton 

Dickinson, 2001. 

§ Sources: Martin DH, Cammarata C, Van der Pol B, et al. Multicenter evaluation of AMPLICOR and automated COBAS AMPLICOR CT/NG tests for Neisseria 

gonorrhoeae. J Clin Microbiol 2000;38:3544–9. Crotchfelt KA, Welsh LE, DeBonville D, Rosenstraus M, Quinn TC. Detection of Neisseria gonorrhoeae and 

Chlamydia trachomatis in genitourinary specimens from men and women by a coamplification PCR assay. J Clin Microbiol 1997;35:1536–40. 

¶ Source: Hook EW III, Ching SF, Stephens J, Hardy KF, Smith KR, Lee HH. Diagnosis of Neisseria gonorrhoeae infections in women by using the ligase chain 

reaction on patient-obtained vaginal swabs. J Clin Microbiol 1997;35:2129–32. 
 

34 MMWR October 18, 2002 

Appendix C 

Conducting Studies To Evaluate Chlamydia trachomatis and Neisseria
 

gonorrhoeae Tests, Including Studies Required by the Regulations
 

of the Clinical Laboratory Improvement Amendments of 1988
 

for Verifying or Establishing Test Performance Characteristics
 

When a test is a candidate to replace an established test, the 

sensitivities and specificities of the candidate and established tests 

should be compared. Recommendations for the conduct of test 

evaluation studies have been reviewed elsewhere (C-1–C-4). The 

imperfect sensitivity and specificity of reference standards complicate evaluation of C. trachomatis and N. gonorrhoeae tests. 

Discrepant analysis has been used universally to address this problem in the past. However, this approach has been criticized because of the likelihood of producing biased estimates of test 

characteristics (C-5–C-8). Key to advancing the evaluation of C. 

trachomatis and N. gonorrhoeae tests is the introduction of study 

designs that compare candidate and established tests in the same 

study by using an independent reference standard or by using 

approaches that do not require designation of a reference standard. Investigation of such designs for evaluation of C. trachomatis 

tests has begun (C-6,C-9–C-15). 

The Clinical Laboratory Improvement Amendments of 1988 

(CLIA) requires that a clinical laboratory verify or establish the 

performance of a test to be used in the medical care of persons 

when it is introduced into that laboratory (C-16). Verification 

of performance under CLIA applies to the introduction of tests 

that are Food and Drug Administration (FDA)-cleared, and the 

CLIA requirement is that the laboratory demonstrate that test 

performance (i.e., accuracy, precision, reportable range of results, 

and appropriate normal values) in that laboratory be equivalent 

to the performance claimed by the manufacturer in the FDAcleared package insert. Establishing performance under CLIA 

applies to tests or modifications of tests that have not been FDAcleared for a particular use. When a modification or use of a test 

has not been FDA-cleared, CLIA requires that the laboratory 

establish the performance characteristics of the test for that use. 

In addition to the performance specifications noted previously, 

establishing performance must include determinations of analytical sensitivity and specificity, to include interfering substances. 

Such verification or establishment studies are relatively straightforward when the candidate test performs similarly to the established test. In such cases, the laboratory can verify or establish 

performance by using the established test as the reference standard if discrepancies between the candidate and established test 

are uncommon. If the candidate test performs differently from 

the established test, the laboratory is faced with the economic 

and logistical challenge of verifying or establishing the performance of the candidate test by introducing an independent reference standard. If the laboratory lacks an independent reference 

standard, a reference laboratory with an independent reference 

standard might be enlisted to 1) blindly test a suitable sample of 

verification or establishment study specimens with the reference 

standard tests or 2) supply a panel of specimens previously characterized by the reference laboratory. The reader is referred to 

the American Society for Microbiology CUMITECH series for 

detailed guidance regarding conduct of verification and establishment studies (C-17). 

References 

C-1. Irwig L, Tosteson ANA, Gatsonis C, et al. Guidelines for meta-analyses 

evaluating diagnostic tests. Ann Intern Med 1994;120:667–76. 

C-2. Noe DA. Evaluation of the medical utility of classification studies 

[Chapter 4]. In: Noe DA, Rock RC, Grochow LB, Kahn SB, Perlin 

E, eds. Laboratory medicine: the selection and interpretation of clinical 

laboratory studies. Baltimore, MD: Williams & Wilkins, 1994:44–52. 

C-3. Noe DA. Diagnostic classification [Chapter 3]. In: Noe DA, Rock 

RC, Grochow LB, Kahn SB, Perlin E, eds. Laboratory medicine: the 

selection and interpretation of clinical laboratory studies. Baltimore, 

MD: Williams & Wilkins, 1994:27–43. 

C-4. Reid MC, Lachs MS, Feinstein AR. Use of methodological standards 

in diagnostic test research: getting better but still not good. JAMA 

1995;274:645–51. 

C-5. Hadgu A. Bias in the evaluation of DNA-amplification tests for detecting Chlamydia trachomatis. Statist Med 1997;16:1391–9. 

C-6. Miller WC. Bias in discrepant analysis: when two wrongs don’t make 

a right. J Clin Epidemiol 1998;51:219–31. 

C-7. Lipman HB, Astles JR. Quantifying the bias associated with use of 

discrepant analysis. Clin Chem 1998;44:108–15. 

C-8. McAdam AJ. Discrepant analysis: how can we test a test? J Clin 

Microbiol 2000;38:2027–9. 

C-9. Alonzo TA, Pepe MS. Using a combination of reference tests to assess 

the accuracy of a new diagnostic test. Statist Med 1999;18:2987–3003. 

C-10. Miller WC. Can we do better than discrepant analysis for new diagnostic test evaluation? [Editorial response]. Clin Infect Dis 

1998;27:1186–93. 

C-11. Johnson RE, Green TA, Schachter J, et al. Evaluation of nucleic acid 

amplification tests as reference tests for Chlamydia trachomatis infections in asymptomatic men. J Clin Microbiol 2000;38:4382–6. 

C-12. Hadgu A, Qu Y. Biomedical application of latent class models with 

random effects. Appl Statist 1998;47(Pt 4):603–16. 

C-13. Qu Y, Hadgu A. Model for evaluating sensitivity and specificity for 

correlated diagnostic tests in efficacy studies with an imperfect reference test. Journal of the American Statistical Association 1998;93:920–8. 

C-14. Cheng H, Macaluso M, Vermund SH, Hook EW III. Relative accuracy of nucleic acid amplification tests and culture in detecting Chlamydia in asymptomatic men. J Clin Microbiol 2001;39:3927–37. 

C-15. Black CM, Marrazzo J, Johnson RE, et al. Head-to-head multicenter 

comparison of DNA probe and nucleic acid amplification tests for 

Chlamydia trachomatis in women with use of an improved reference 

standard. J Clin Microbiol (in press). 

C-16. Code of Federal Regulations. Title 42, Chapter IV, part 493—Laboratory requirements. 

C-17. Elder BL, Hansen SA, Kellogg JA, Marsik FJ, Zabransky RJ. Verification and validation of procedures in the clinical microbiology laboratory [31]. In: McCurdy BW, ed. CUMITECH: cumulative 

techniques and procedures in clinical microbiology. Washington, DC: 

American Society for Microbiology, 1997. 
Vol. 51 / RR-15	 Recommendations and Reports 35 

Appendix D 

Recommendations for Transport and Storage of Specimens for Chlamydia 

trachomatis and Neisseria gonorrhoeae Testing, by Testing Procedure Type 

Readers are cautioned to refer to the manufacturers’ test kit inserts for specific details. Information in this appendix represents 

general conditions for comparative purposes. 

Intended Laboratory 

Procedure Specimen Transport Storage 

Culture isolation 

•	 C. trachomatis 

Culture isolation 

•	 N. gonorrhoeae 

Direct fluorescent antibody 

•	 C. trachomatis 

Immunoassays (enzyme 

immunoassay or 

optical immunoassay) 

•	 C. trachomatis 

Swab* 

•	 Cotton 

•	 Rayon 

•	 Dacron® 

•	 Cytobrush 

Swab 

•	 Rayon 

•	 Dacron 

•	 Calcium alginate 

Swab 

•	 Cotton 

•	 Rayon 

•	 Dacron 

•	 Calcium alginate 

•	 Cytobrush 

Swab 

•	 Manufacturersupplied 

•	 <24 hours at 4o

C 

•	 If delayed >24 hours, freeze to 

–70o

C 

• Transport media† 

Sucrose phosphate (2SP) or sucrose phosphate glutamate (SPG), 

supplemented with 5% fetal bovine serum, 10 μg/mL gentamicin, 

100 μg/mL vancomycin, and 1 μg/ 

mL amphotericin B 

Micro test Multi-Microbe Media 

(M4; manufactured by Micro Test, 

Inc., Lilburn, GA) 

•	 <5 hours 

Inoculate selective or nonselective 

medium and incubate at 35o

C– 

36.5o

C and place immediately in 

a CO2-enriched atmosphere 

•	 5–48 hours 

Can be transported in ambient air 

and temperature if inoculated medium has been incubated at 35o

C– 

36.5oC in a CO2-enriched 

atmosphere for 18–24 hours before transport 

•	 Do not refrigerate 

•	 Prepare slides immediately after 

specimen collection 

•	 Air dry and fix slide for 10 minutes in alcohol or acetone 

•	 Transport to laboratory <7 days at 

room temperature or 4o

C 

•	 <24 hours at room temperature 

•	 <5 days at 2o

C–8oC 

•	 Do not freeze specimens 

• Frozen to –70o

C in transport 

media 

•	 Viability remains after >2 

years, if frozen correctly 

• Avoid storage at –20o

C or in 

frost-free freezers 

•	 Must be subcultured every 

18–24 hours to maintain 

viability until frozen 

•	 Should be stored frozen to 

<–70oC in trypticase soy 

broth plus 20% glycerine 

•	 Fixed and unstained slides 

can be stored at –20o

C for >2 

years 

•	 Specimens must be processed 

<5 days after collection 

•	 Storage after processing is not 

applicable 
36 MMWR October 18, 2002 

Intended Laboratory 

Procedure Specimen Transport Storage 

Nucleic acid probes 

•	 C. trachomatis 

•	 N. gonorrhoeae 

Nucleic acid amplification 

•	 C. trachomatis 

•	 N. gonorrhoeae 

— 

Swab 

•	 Manufacturersupplied 

Swab 

•	 Manufacturersupplied 

Urine 

•	 <7 days at 2o

C–25oC 

•	 Swab must be immersed in 

manufacturer-supplied medium 

• <5 days at 2o

C–27oC; <7 days if 

maintained at 2o

C–8oC 

•	 Swab must be immersed in 

manufacturer-supplied medium 

or in isolation transport medium 

•	 <24 hours at room temperature 

•	 <5 days at 2o

C–8oC 

•	 Specimens can be frozen to 

<–20o

C and tested <60 days after collection 

•	 Specimens can be frozen to 

–70o

C and tested <60 days 

after collection 

•	 Specimens can be frozen to 

–20o

C and tested <60 days 

after collection 

•	 Manufacturer for the strand 

displacement assay does not 

recommend freezing specimens 

* New lots of swabs should be checked for toxicity to C. trachomatis isolation. Swabs with wooden shafts might be toxic to C. trachomatis or tissue culture cells. 

† Not intended as a compendium of commercially available transport media. 
Vol. 51 / RR-15	 Recommendations and Reports 37 

Appendix E
 

Chlamydia trachomatis Screening Recommendations
 

The U.S. Preventive Services Task Force (USPSTF) has published recommendations for screening certain groups of women 

for C. trachomatis infection (E-1). The following summarizes 

those recommendations: 

•	 Routinely screen all sexually active women aged <25 years 

for C. trachomatis infection, whether or not they are pregnant. Women and adolescents aged <20 years are at highest risk for chlamydial infection, but the majority of 

reported data indicate that infection is prevalent among 

women aged 20–25 years. More targeted screening might 

be indicated by local prevalence data. 

•	 Screening of women aged >25 years for C. trachomatis 

should also be considered if they are at increased risk. 

•	 Prevalence of C. trachomatis infection varies widely among 

communities and patient populations. Knowledge of the 

patient population is the best guide to developing a screening strategy. Certain risk factors should be considered, 

including 

— having new or multiple sex partners,* 

— having a prior history of a sexually transmitted 

disease,† and 

— not using condoms consistently and correctly. 

•	 Personal risk depends on the number of risk markers and 

local disease prevalence. Specific risk-based protocols need 

to be tested locally. 

•	 The optimal timing of screening in pregnancy is 

uncertain. 

* USPSTF does not include a time interval for this risk factor. Having new or 

multiple sex partners within the past 90 days was the criterion recommended 

previously by CDC (Source: CDC. Recommendations for the prevention and 

management of Chlamydia trachomatis infections, 1993. MMWR 

1993;42[No. RR-12]:1–39). A history of new or multiple sex partners since 

the woman’s last screening would also provide a time interval for previously 

screened women. 

† USPSTF did not include a time limitation for the risk factor of having a prior 

history of sexually transmitted disease. Obtaining a history of a sexually 

transmitted disease within the past year includes an arbitrary choice of time 

interval. Obtaining a history of a sexually transmitted disease since the woman’s 

last screening would also restrict the time interval for a sexually transmitted 

disease in the past. 

— Screening early in pregnancy provides increased 

opportunities to improve pregnancy outcomes, including low birth weight and premature delivery. 

— Screening and treatment in the third trimester might 

be more effective at preventing transmission of chlamydial infection to the infant during birth by reducing 

the risk for reinfection. 

— The incremental benefit of repeated screening is 

unknown. 

•	 The optimal interval for screening women with a previous negative screening test is uncertain. The interval for 

rescreening should be based on changes in sexual partners, young age, and other C. trachomatis risk factors. If 

evidence exists that a woman is at low risk for infection 

(e.g., in a mutually monogamous relationship with a previous history of negative screening tests for chlamydial 

infection), screening frequently might be unnecessary. 

USPSTF did not address screening of women with a 

C. trachomatis infection. CDC recommends that women with 

C. trachomatis infection be screened 3–4 months after treatment is completed (E-2). 

References 

E-1.US Preventive Services Task Force. Screening for chlamydial infection: 

recommendations and rationale. Am J Prev Med 2001;20(3Suppl):90–4. 

E-2.CDC. Sexually transmitted diseases treatment guidelines. MMWR 

2002;51(No. RR-6):1–80. 
38 MMWR October 18, 2002 

Appendix F
 

Characteristics of Neisseria and Related Species of Human Origin*
 

Species 

Acid from Reduction 

Polysaccharide 

from Tributyrin 

Glucose Maltose Lactose Sucrose Fructose of nitrate sucrose hydrolysis 

N. gonorrhoeae† 

N. meningitidis 

N. lactamica 

N. cinerae§ 

N. polysaccharea 

N. subflava¶ 

N. sicca 

N. mucosa 

N. flavescens 

N. elongata** 

Branhamella 

catarrhalis 

Kingella denitrificans 

+ 

+ 

+ 

– 

+ 

+ 

+ 

+ 

– 

– 

– 

+ 

– 

+ 

+ 

– 

+ 

+ 

+ 

+ 

– 

– 

– 

– 

– 

– 

+ 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

V 

+ 

+ 

– 

– 

– 

– 

– 

– 

– 

– 

– 

V 

+ 

+ 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

+ 

– 

– 

+ 

+ 

– 

– 

– 

– 

– 

V 

+ 

+ 

+ 

–

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

–

+ 

– 

* N. gonorrhoeae contains a subspecies referred to as N. kochii; isolates of this subspecies exhibit characteristics of both N. gonorrhoeae and N. meningitidis 

but will be identified as N. gonorrhoeae by tests routinely used for the identification of Neisseria species. 

† Symbols: +, strains typically positive but genetic mutants might be negative; –, negative; and V, strain-dependent.
 § Certain strains grow on selective media for isolation of N. gonorrhoeae.
 ¶ Includes biovars subflava, flava, and perflava. Neisseria subflava biovar perflava strains produce acid from sucrose and fructose and produce polysaccharide from sucrose; Neisseria subflava biovar flava strains produce acid from fructose; Neisseria subflava biovar flava and Neisseria subflava biovar 

subflava do not produce polysaccharide. 

** Rod-shaped organism. Catalase test is weakly positive or negative compared with those of other Neisseria species (catalase positive). Results in this 

table are for N. elongata subspecies elongata. Strains of N. elongata subspecies glycolytica might produce a weak acid reaction from D-glucose, are 

catalase-positive, and do not reduce nitrate but do reduce nitrite. Strains of N. elongata subspecies nitroreducans (formerly CDC group M-6) might 

produce a weak acid reaction from D-glucose, are catalase-negative, and reduce nitrate and nitrite. 
Vol. 51 / RR-15 Recommendations and Reports 39 
40 MMWR October 18, 2002 
 

Morbidity and Mortality Weekly Report
 

Recommendations and Reports	 October 18, 2002 / Vol. 51 / No. RR-15 

Continuing Education Activity Sponsored by CDC 

Screening Tests To Detect Chlamydia trachomatis 

and Neisseria gonorrhoeae Infections — 2002 

EXPIRATION — October 18, 2005 

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instruct you to “Indicate all that apply.” 5. Sign and date the response form or a photocopy of the form and send no later 

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Centers for Disease Control and Prevention
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SAFER• • HEALTHIER•PEOPLETM
 
CE-2	 MMWR October 18, 2002 

GOAL AND OBJECTIVES
 

This MMWR provides recommendations regarding laboratory tests for Chlamydia trachomatis and Neisseria gonorrhoeae infections. These recommendations were prepared 

by CDC staff in the Division of AIDS, STD, and TB Laboratory Research, National Center for Infectious Diseases, and the Division of STD Prevention, National Center 

for HIV, STD, and TB Prevention after a literature review and consultation with specialists within and outside CDC. The goal of this report is to provide guidance regarding 

selecting and using laboratory tests for C. trachomatis and N. gonorrhoeae infections, with an emphasis on screening men and women in the United States. Upon completion 

of this educational activity, the reader should be able to 1) describe the morbidity associated with C. trachomatis and N. gonorrhoeae infections that has resulted in 

establishment of national prevention programs, 2) list the categories of tests available for detecting C. trachomatis and N. gonorrhoeae infections, 3) apply test performance 

and other criteria to selecting C. trachomatis and N. gonorrhoeae screening tests, and 4) apply recommendations for implementing and using C. trachomatis and N. gonorrhoeae 

screening tests. 

To receive continuing education credit, please answer all of the following questions. 

1.	 Which of the following conditions is not an adverse consequence of a 

C. trachomatis or N. gonorrhoeae infection? 

A.	 Infertility. 

B.	 Pelvic inflammatory disease. 

C. Pyelonephritis. 

D. Infant pneumonia. 

E.	 Ectopic pregnancy. 

2.	 Which of the following does not apply to the recommendations of the 

Third U.S. Preventive Services Task Force for screening persons for C. 

trachomatis infection? 

A.	 Sexually active women aged <25 years should be screened, unless local 

data indicate otherwise. 

B.	 Sexually active adolescent females are at lower risk than older women 

(e.g., women aged 20–25 years). 

C. Rescreening of women with 	C. trachomatis infection might be 

indicated because of a high rate of reinfection. 

D.	 Screening of men is of potential utility as a result of new screening tests, 

but screening criteria have not been adequately evaluated. 

3.	 Which of the following is an advantage of nucleic acid amplification tests? 

A.	 Higher test sensitivity. 

B.	 Ability to use a urine specimen. 

C. Lower cost per test. 

D. Ability to test for N. gonorrhoeae by using the same specimen. 

E.	 Reduced requirements for quality assurance. 

F.	 A, B, and D are advantages, but not C and E. 

4.	 Which of the following statements best describes the positive 

predictive value (PPV) of a diagnostic test? 

A.	 PPV is the proportion of persons who have a positive test among those 

who actually have the condition for which the test is performed. 

B.	 PPV is the proportion of persons who actually have the condition 

among all persons who have a positive test. 

C. PPV is the proportion of persons who have a negative test among those 

who do not have the condition. 

D.	 PPV is the proportion of persons who do not have the condition 

among all persons who have a negative test. 

5.	 An additional test after a positive screening test for C. trachomatis or N. gonorrhoeae infection should be considered when the . . . 

A.	 prevalence of infection is low. 

B.	 sensitivity of the screening test is low. 

C. specificity of the screening test is not sufficiently high. 

D. PPV of the screening test is thought to be low. 

E.	 A, C, and D, but not B. 

F.	 B, C, and D, but not A. 

6.	 Which of the following methods of additional testing after a positive 

screening test for C. trachomatis or N. gonorrhoeae infection is 

theoretically most accurate? 

A.	 Repeat the screening test on the original specimen. 

B.	 Repeat the screening test on the original specimen with the addition of 

a blocking or competition reagent. 

C. Retest the original specimen with a test that identifies a different target 

or trait and uses a different format than the screening test. 

D.	 Obtain a fresh specimen and test with an alternative test that identifies 

a different target or trait and uses a different format than the original 

screening test. 

7.	 Which of the following statements characterizes economic analyses 

conducted to assist in selecting a screening test for C. trachomatis or 

N. gonorrhoeae infection? 

A.	 The cost of additional testing after a positive screening test is usually 

only a limited proportion of the costs of screening and treatment. 

B.	 The cost of screening tests performed in the absence of symptoms or 

signs of C. trachomatis or N. gonorrhoeae infection is usually 

reimbursed by insurance. 

C. A screening program is cost-effective only if it is also cost-saving. 

D.	 Economic analyses can be conducted from a societal or a health-care 

provider perspective. 

E.	 A and D, but not B and C. 

F.	 A, C, and D, but not B. 

8.	 Which of the following is a reason to recommend culture for the 

detection of N. gonorrhoeae infection? 

A.	 Additional testing might be required to establish a diagnosis. 

B.	 Treatment failures have been reported because of decreased 

susceptibility of N. gonorrhoeae to the antibiotic used for treatment. 

C. The location for specimen collection and the laboratory are relatively 

far apart geographically. 

D.	 Given appropriate transport conditions, culture is as sensitive or 

approximately as sensitive as alternative tests. 

E.	 A, B, and D but not C. 

9.	 Which of the following is a characteristic of point-of-care tests for C. 

trachomatis infection? 

A.	 Sensitivities of point-of-care tests are higher than tests designed to be 

performed in batch after the tested person leaves. 

B.	 Point-of-care tests are useful for increasing the percent of test-positive 

persons who receive treatment. 

C. A lower cost per tested person has been a principal reason for screening 

with point-of-care tests. 

10. Which of the following statements concerning the collection of 

endocervical swab specimens for C. trachomatis tests is true? 

A.	 Specimens for nonculture tests should be obtained by following the 

directions outlined by manufacturers in package inserts. 

B.	 Studies have reported that obtaining endocervical swab specimens 

with adequate numbers of columnar epithelial cells is critical even for 

nucleic acid amplification tests. 

C. Clinicians require training and periodic assessment to maintain correct 

endocervical specimen collection technique. 

D. All of the statements are true. 

11. Indicate your work setting. 

A.	 State/local health department. 

B.	 Other public health setting. 

C. Hospital clinic/private practice. 

D. Managed care organization. 

E.	 Academic institution. 

F.	 Other. 
MMWR Response Form for Continuing Education Credit

October 18, 2005/Vol. 51/No. RR-15

Laboratory Guidelines for Screening To Detect Chlamydia

trachomatis and Neisseria gonorrhoeae Infections — 2002

To receive continuing education credit, you must

provide your contact information; 1. 

indicate your choice of CME, CEU, or CNE credit; 2.

3. answer all of the test questions;

sign and date this form or a photocopy; 4. 

submit your answer form by October 18, 2005.
 5.

Failure to complete these items can result in a delay or rejection of


your application for continuing education credit.


Check One

Last Name First Name CME Credit

CEU Credit

CNE Credit Street Address or P.O. Box

Apartment or SuiteCity State ZIP Code Phone Number Fax Number E-Mail Address

Fill in the appropriate blocks to indicate your answers. Remember, you must answer all of the questions toreceive continuing education credit!

1. [ ] A [ ] B [ ] C [ ] D [ ] E 14. [ ] A [ ] B [ ] C [ ] D [ ] E 2. [ ] A [ ] B [ ] C [ ] D 15. [ ] A [ ] B [ ] C [ ] D 3. [ ] A [ ] B [ ] C [ ] D [ ] E [ ] F 16. [ ] A [ ] B [ ] C [ ] D [ ] E 4. [ ] A [ ] B [ ] C [ ] D 17. [ ] A [ ] B [ ] C [ ] D [ ] E 5. [ ] A [ ] B [ ] C [ ] D [ ] E [ ] F 18. [ ] A [ ] B [ ] C [ ] D [ ] E 6. [ ] A [ ] B [ ] C [ ] D 19. [ ] A [ ] B [ ] C [ ] D [ ] E 7. [ ] A [ ] B [ ] C [ ] D [ ] E [ ] F 20. [ ] A [ ] B [ ] C [ ] D [ ] E 8. [ ] A [ ] B [ ] C [ ] D [ ] E 21. [ ] A [ ] B [ ] C [ ] D [ ] E 9. [ ] A [ ] B [ ] C 22. [ ] A [ ] B [ ] C [ ] D [ ] E 

10. [ ] A [ ] B [ ] C [ ] D 23. [ ] A [ ] B [ ] C [ ] D [ ] E 11. [ ] A [ ] B [ ] C [ ] D [ ] E [ ] F 24. [ ] A [ ] B [ ] C [ ] D [ ] E 12. [ ] A [ ] B [ ] C [ ] D [ ] E [ ] F 25. [ ] A [ ] B [ ] C [ ] D [ ] E 13. [ ] A [ ] B [ ] C [ ] D [ ] E 26. [ ] A [ ] B [ ] C [ ] D [ ] E [ ] F 

Detach or photocopy. 

Signature Date I Completed Exam 

Vol. 51 / No. RR-15 Recommendations and Reports CE-3 

12. Which best describes your professional activities? 16. After reading this report, I am confident I can describe how to select 

A. Patient care — emergency/urgent care department. and use laboratory tests for C. trachomatis and N. gonorrhoeae 

B. Patient care — inpatient. infections, with an emphasis on screening men and women in the 

C. Patient care — primary-care clinic or office. United States. 

D. Laboratory/pharmacy. A. Strongly agree. 

E. Public health. B. Agree. 

F. Other. C. Neither agree nor disagree. 

D. Disagree. 13. I plan to use these recommendations as the basis for . . . (Indicate all E. Strongly disagree. that apply.) 

A. health education materials. 17. After reading this report, I am confident I can describe the morbidity 

B. insurance reimbursement policies. associated with C. trachomatis and N. gonorrhoeae infections that has 

C. local practice guidelines. resulted in the establishment of national prevention programs. 

D. public policy. A. Strongly agree. 

E. other. B. Agree. 

C. Neither agree nor disagree. 14. Each month, approximately how many patients do you test for C. D. Disagree. Trachomatis or N. gonorrhoeae infections? E. Strongly disagree. A. None. 

B. 1–10. 18. After reading this report, I am confident I can list the categories of tests 

C. 11–100. available to detect C. trachomatis and N. gonorrhoeae infections. 

D. 101–1,000. A. Strongly agree. 

E. >1,000. B. Agree. 

C. Neither agree nor disagree. 15. How much time did you spend reading this report and completing the D. Disagree. exam? E. Strongly disagree. A. <2.0 hours. 

B. >2.0 hours but <3.0 hours. 

C. >3.0 but <4.0 hours. 

D. >4.0 hours. 
CE-4 MMWR October 18, 2002 

19. After reading this report, I am confident I can apply test performance 

and other criteria to selecting C. trachomatis and N. gonorrhoeae 

screening tests. 

A. Strongly agree. 

B. Agree. 

C. Neither agree nor disagree. 

D. Disagree. 

E. Strongly disagree. 

20. After reading this report, I am confident I can apply recommendations 

for the implementation and use of C. trachomatis and N. gonorrhoeae 

screening tests. 

A. Strongly agree. 

B. Agree. 

C. Neither agree nor disagree. 

D. Disagree. 

E. Strongly disagree. 

21. The objectives are relevant to the goal of this report. 

A. Strongly agree. 

B. Agree. 

C. Neither agree nor disagree. 

D. Disagree. 

E. Strongly disagree. 

22. The tables, boxes, and figure are useful. 

A. Strongly agree. 

B. Agree. 

C. Neither agree nor disagree. 

D. Disagree. 

E. Strongly disagree. 

23. Overall, the presentation of the report enhanced my ability to 

understand the material. 

A. Strongly agree. 

B. Agree. 

C. Neither agree nor disagree. 

D. Disagree. 

E. Strongly disagree. 

24. These recommendations will affect my practice. 

A. Strongly agree. 

B. Agree. 

C. Neither agree nor disagree. 

D. Disagree. 

E. Strongly disagree. 

25. The availability of continuing education credit influenced my decision 

to read this report. 

A. Strongly agree. 

B. Agree. 

C. Neither agree nor disagree. 

D. Disagree. 

E. Strongly disagree. 

26. How did you learn about this continuing education activity? 

A. Internet. 

B. Advertisement (e.g., fact sheet, MMWR cover, newsletter, or journal). 

C. Coworker/supervisor. 

D. Conference presentation. 

E. MMWR subscription. 

F. Other. 

Correct answers for questions 1–10 

C; 2. B; 3. F; 4. B; 5. E; 6. D; 7. E; 8. E; 9. B; 10. D. 1.
Laboratory Guidelines for Screening To Detect Chlamydia trachomatis
 

and Neisseria gonorrhoeae Infections — 2002
 

Consultants
 

External Consultants: Association of Public Health Laboratories, Washington, D.C. (no reviewers identified); Dana Best, M.D., Agency for Healthcare 

Research and Quality, Rockville, Maryland; Margaret C. Fisher, M.D., and Leonard Weiner, M.D., American Academy of Pediatrics, Elk Grove Village, 

Illinois; Luella Klein, M.D., American College of Obstetricians and Gynecologists, Washington, D.C.; Roxanne Shively, Food and Drug Administration, 

Rockville, Maryland; Aggie Clark, University of Washington, Seattle, Washington; Dennis V. Ferrero, M.P.H., San Joaquin County Regional Public Health 

Laboratory, Stockton, California; Charlotte A. Gaydos, Dr.P.H., Johns Hopkins University, Baltimore, Maryland; Anne Haddix, Ph.D., Emory University, 

Atlanta, Georgia; Margaret R. Hammerschlag, M.D., State University of New York, Brooklyn, New York; Doug R. Harger, Oregon Health Division, Portland, 

Oregon; Edward W. Hook, III, M.D., University of Alabama at Birmingham, Birmingham, Alabama; J. Mehsen Joseph, Ph.D., Maryland Department of 

Health and Mental Hygiene, Baltimore, Maryland; Robert B. Jones, M.D., Ph.D., Indiana University, Indianapolis, Indiana; James A. Kellogg, Ph.D., York 

Hospital, York, Pennsylvania; Barry P. Katz, Ph.D., Indiana University, Indianapolis, Indiana; David H. Martin, M.D., Louisiana State University, New 

Orleans, Louisiana; Toby Merlin, M.D., Lovelace Health Systems and CIGNA Healthcare of Arizona, Albuquerque, New Mexico; William C. Miller, M.D., 

Ph.D., University of North Carolina, Chapel Hill, North Carolina; Pamela G. Nathanson, Family Planning Council, Inc., Philadelphia, Pennsylvania; Albert 

Rabinovitch, M.D., Ph.D., Specialty Laboratories, Inc., Santa Monica, California; Julius Schachter, Ph.D., University of California at San Francisco, San 

Francisco, California; Karla Schmitt, Ph.D., Florida Department of Health, Tallahassee, Florida; Michael R. Skeels, Ph.D., Oregon State Public Health 

Laboratories, Portland, Oregon; Walter E. Stamm, M.D., University of Washington, Seattle, Washington; Barbara van der Pol, Indiana University, Indianapolis, 

Indiana; Jo Ann Yatabe, Ph.D., Specialty Laboratories, Inc., Santa Monica, California. 

CDC Consultants: Timothy A. Green, Ph.D., Epidemiology Program Office, John R. Astles, Ph.D., Nancy L. Anderson, M.M.Sc., and Rhonda S. Whalen, 

M.S., Public Health Practice Program Office. 

All MMWR references are available on the Internet at http://www.cdc.gov/mmwr. Use the search function to find specific articles. 

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