7

Technical Notes
8
9

Technical Notes

National Tuberculosis Surveillance System

Reporting areas (i.e., the 50 states, the District of 

Columbia (DC), New York City, Puerto Rico, and 

other U.S. jurisdictions in the Pacific Ocean and 

Caribbean Sea) provide information regarding 

tuberculosis (TB) cases to CDC’s National TB 

Surveillance System (NTSS) by using a standard 

case report form, Report of Verified Case of Tuberculosis (RVCT). TB cases are verified according to the Tuberculosis Case Definition for Public 

Health Surveillance (Appendix A). TB cases are 

reported and counted according to the Recommendations for Reporting and Counting Tuberculosis Cases (Appendix B).

TB Case Definition

In 2009, the TB case definition was modified. 

TB cases are verified according to the following 

specified laboratory and clinical criteria (see Appendix A).

Laboratory Criteria for Diagnosis

A TB case may be verified by the laboratory case 

definition with at least one of the following criteria: (1) isolation of Mycobacterium tuberculosis

complex from a clinical specimen; or (2) demonstration of M. tuberculosis complex from a clinical specimen by nucleic acid amplification test 

(NAAT), or (3) demonstration of acid-fast bacilli 

(AFB) in a clinical specimen when a culture has 

not been or cannot be obtained or is falsely negative or contaminated.

Clinical Case Criteria

A TB case may be verified by the clinical case 

definition in the presence of all of the following 

clinical criteria: (1) a positive tuberculin skin test 

(TST) result or positive interferon gamma release 

assay (IGRA) result for M. tuberculosis; and (2) 

other signs and symptoms compatible with TB 

(e.g., abnormal chest radiograph, abnormal chest 

computerized tomography [CT] scan, or other 

chest imaging study or clinical evidence of current disease); and (3) treatment with two or more 

anti-TB drugs; and (4) a completed diagnostic 

evaluation.

Provider Diagnosis

Provider diagnosis is not a component of the 

case definition for TB as described in Appendix 

A. However, when cases of TB are diagnosed 

but do not meet either the clinical or laboratory 

case definition, reporting areas have the option 

of verifying TB cases on the basis of provider 

diagnosis as described in Appendix B. Through 

2008, the RVCT did not collect information regarding IGRA results. If an IGRA was performed 

in lieu of TST, the RVCT would have indicated 

that TST was not performed. Thus, culture- and 

smear-negative cases without a TST that were 

diagnosed by a positive IGRA result before 

2008 were considered to have been confirmed 

by provider diagnosis. Starting in 2009, positive 

results for an IGRA have been included as part of 

the clinical case definition for TB confirmation. 

Anergic patients with a clinical presentation consistent with TB but without laboratory evidence 

of M. tuberculosis complex would also be an 

example of provider diagnosis and one that has 

not changed over time.

TB Case Verification Criteria Calculation

The software for TB surveillance developed by 

CDC includes a calculated variable for TB case 

verification called “Vercrit,” which was modified 

in 2009. The new variables, Nucleic Acid Amplification Test (NAAT) Result, Interferon Gamma 

Release Assay (IGRA) for Mycobacterium tuberculosis at Diagnosis, and Initial Chest CT Scan 

or Other Chest Imaging Study were added in the 

Vercrit calculation.

Vercrit is calculated by using the following criteria in hierarchical order:

1. Positive culture.

2. Positive NAAT.

3. Positive AFB.

4. Clinical case confirmation.

5. Provider diagnosis.

Reporting and Counting of TB Cases

In 2009, the recommendations for reporting and 

counting of TB cases (Appendix B) were modi-
10

fied. TB cases that are verified but not countable 

for morbidity statistics are now reported to CDC 

as a measure of programmatic and case management burden. However, data for noncountable 

TB cases are incomplete and therefore are not 

included in this report.

The recommendations for counting TB cases 

among immigrants, refugees, and foreign visitors were revised on the basis of the 2007 recommendations in the Technical Instructions for 

Tuberculosis Screening and Treatment for Panel 

Physicians.

1

 Regardless of panel physician classification or citizenship status, immigrants and 

refugees examined after arriving in the United 

States and receiving a diagnosis of clinically active TB requiring anti-TB medications should be 

reported and counted by the locality of their residence at the time of diagnosis. Foreign visitors 

with diagnosed TB receiving anti-TB therapy 

and planning to remain in the United States for 

≥90 days should be reported and counted by the 

locality of current residence.

RVCT Variables

Data regarding demographic characteristics, 

clinical or laboratory diagnosis, initial treatment, 

and treatment outcomes are collected through the 

following three RVCT data collection reports:

1. Report of Verified Case of Tuberculo- 

 sis — used for all patients with a verified 

 TB case.

2. Initial Drug Susceptibility Report 

 (Follow-Up Report 1) — used for all 

 patients who had a culture that was posi- 

 tive for M. tuberculosis complex.

3. Case Completion Report (Follow-Up 

 Report 2) — used for all patients who 

 were alive when TB was diagnosed.

1

CDC. Immigration Requirements: Technical Instructions for Tuberculosis Screening and Treatment 2009. Atlanta: CDC, 

Division of Global Migration and Quarantine, revised October, 2009; http://www.

cdc.gov/immigrantrefugeehealth/pdf/

tuberculosis-ti-2009.pdf.

The instructions for completing the RVCT forms 

and the definitions for all data items are available 

in Centers for Disease Control and Prevention 

(CDC). Report of Verified Case of Tuberculosis 

(RVCT) Instruction Manual. Atlanta, GA: U.S. 

Department of Health and Human Services, 

CDC; 2009. Available at: http://www.cdc.gov/tb/

programs/rvct/InstructionManual.pdf.

Tabulation and Presentation of TB Data

This report presents summary data for TB cases 

counted by reporting areas through the end of 

2016. TB cases are tabulated by year in which 

the reporting area verified that the patient had 

TB and included the patient in its official annual 

TB case count. Since 2004, the published report 

has reflected updated information regarding the 

numbers of cases of confirmed TB for each year 

from 1993 onward. Totals for the United States 

include data from the 50 states and DC.

Trend data are presented in Tables 1–15. Age 

group tabulations are based on the patient’s age 

during the month and year the patient was reported to the health department as having a suspected TB case. State or metropolitan area data 

tabulations are based on the patient’s residence at 

the time of TB diagnosis.

Rates

Rates are expressed as the number of cases 

reported each calendar year per 100,000 persons. 

Population denominators used in calculating TB 

rates were based on official census and midyear postcensal estimates from the U.S. Census 

Bureau. In Tables 1, 29, and 30, the U.S. total 

populations for 1990–1999 were taken from the 

Bridged-Race Intercensal Population Estimates 

for July 1, 1990–July 1, 1999 (ftp://ftp.cdc.gov/

pub/health_statistics/nchs/datasets/nvss/bridgepop/documentationbridgedintercena1.doc); 

populations for 2000–2009 were taken from the 

U.S. Census Intercensal Estimates of the Resident Population for the United States, Regions, 

States, and Puerto Rico for April 1, 2000–July 1, 

2010 (https://www.census.gov/data/tables/timeseries/demo/popest/intercensal-2000-2010-state.
11

html); and populations for 2010–2016 were 

taken from the U.S. Census Annual Estimates of 

the Resident Population for the United States, 

Regions, States, and Puerto Rico: April 1, 2010 

to July 1, 2016 (https://www2.census.gov/

programs-surveys/popest/tables/2010-2016/state/

totals/nst-est2016-01.xlsx). Beginning in 2004, 

unrounded numbers were applied to calculate the 

annual percentage change in the TB case rate.

During 2003, two modifications were made to 

the RVCT form: (1) entries for multiple race 

(two or more races reported for a person) were 

allowed, and (2) the previous category of “Asian/

Pacific Islander” was divided into “Asian” and 

“Native Hawaiian/Other Pacific Islander.” To 

calculate rates for Tables 2 and 4, denominators for 1993–1999 were obtained from the U.S. 

Census Monthly Postcensal Resident Population, 

by single year of age, sex, race, and Hispanic 

origin (https://www.census.gov/data/datasets/

time-series/demo/popest/1990s-national.html); 

denominators for 2000–2009 were obtained 

from U.S. Census Intercensal Estimates of the 

Resident Population by Sex, Race, and Hispanic 

Origin for the United States: April 1, 2000 to 

July 1, 2010 (https://www.census.gov/data/

datasets/time-series/demo/popest/intercensal2000-2010-state.html); and denominators for 

2010–2016 were obtained from the U.S. Census 

Annual Estimates of the Resident Population by 

Sex, Race, and Hispanic Origin: April 1, 2010 

to July 1, 2016 (https://www.census.gov/data/

tables/2016/demo/popest/nation-detail.html).

The population source for nativity is the Current 

Population Survey, which is used to calculate 

case rates for U.S.- and non-U.S.–born persons with diagnosed TB. U.S.-born populations 

includes persons born in the 50 states and DC, 

those born abroad to U.S. parents, and those born 

in U.S. territories. In Table 5, the populations for 

U.S.- and non-U.S.–born persons for 1993 were 

obtained from Quarterly Estimates of the United 

States Foreign-born and Native Resident Populations: April 1, 1990–July 1, 1999 (http://www.

census.gov/population/estimates/nation/nativity/

fbtab001.txt). Denominators for computing the 

1994–2016 rates were based on extrapolations 

from the U.S. Census Current Population Survey (accessed July 2016) through DataFerrett at: 

http://dataferrett.census.gov/). Denominators for 

computing 2016 rates in Table 17 were obtained 

from U.S. Census Annual Estimates of the 

Resident Population by Sex, Race, and Hispanic 

Origin: April 1, 2010 to July 1, 2016 (https://

www.census.gov/data/tables/2016/demo/popest/

nation-detail.html).

Mortality Data

The annual mortality rate is calculated as the 

number of deaths caused by TB in that year, 

divided by the estimated population for the year, 

multiplied by 100,000 (Table 1). The number of 

deaths was obtained from the CDC’s National 

Center for Health Statistics, Multiple Cause of 

Death Files, 1999–2015, available from CDC’s 

WONDER online database and released in 2017. 

Data were compiled from the 57 vital statistics 

jurisdictions through the Vital Statistics Cooperative Program. Finalized numbers of TB-related 

deaths for 2016 were unavailable at the time of 

this publication.

Drug Resistance

Drug-resistance patterns are displayed in separate tables with drug-resistance trend data by 

previous TB status and origin of birth. Isoniazid 

resistance and multidrug resistance are displayed 

in Tables 8 and 9, respectively.

Completion of Tuberculosis Therapy

Tables 10, 57, 58, and 59 present percentages of 

completion of TB therapy (COT). Data collected 

by RVCT Follow Up Report-2 forms regarding 

date and reason therapy was stopped (e.g., the 

patient completed the therapy or the patient died) 

were used to calculate COT percentages. Cases 

were stratified by the indicated length of therapy, 

based on American Thoracic Society, CDC, and 

Infectious Diseases Society of America treatment 

guidelines in effect during the period covered 
12

and the patient’s initial drug-susceptibility test 

results, age, and disease site.2

In Table 58, the first column lists the total number of cases reported during 2014. The remaining columns are grouped under two headings: 

therapy of ≤1 year indicated and therapy of >1 

year indicated. Patients eligible to complete 

therapy in ≤1 year had to have been alive at 

time of diagnosis and initiated therapy with ≥1 

drug. Eligible patients did not have rifampin 

resistance; did not die in ≤1 year after initiating 

therapy; did not move out of the country in ≤1 

year after initiating therapy; and did not have 

meningeal TB, bone or joint TB, or TB of the 

central nervous system, regardless of age. Additionally, TB patients aged 0–14 years were 

ineligible to complete therapy in ≤1 year if they 

had disseminated disease (defined as miliary TB, 

a positive TB blood culture, or a positive NAAT 

on a blood specimen). Patients with culturenegative disease, those with an unknown culture 

status, and those with culture-positive disease 

but unknown initial drug-susceptibility test results were included under the category of therapy 

of ≤1 year indicated.

For the group with an indicated length of therapy 

of ≤1 year, percentages are displayed for both 

COT in ≤1 year and for COT regardless of 

duration (i.e., duration of therapy ≤1 year or >1 

year). For COT ≤1 year, the numerator included 

only those patients completing therapy in ≤366 

days (based on the dates therapy was started 

and stopped). Patients with missing dates were 

classified as “treatment not completed” for this 

calculation.

COT percentages, regardless of duration, were 

calculated by dividing the number of patients 

reported as having completed therapy by the 

number of total eligible patients. Patients with 

an outcome other than completed therapy (i.e., 

2

CDC. Treatment of Tuberculosis, American 

Thoracic Society, CDC, and the Infectious 

Diseases Society of America. MMWR 2003; 52 

(No. RR-11): 1–77.

moved, lost to follow-up, refused treatment, or 

other) were classified as “treatment not completed.” Patients with an unknown outcome were 

also classified as “treatment not completed.” For 

the group of indicated therapy length >1 year, 

only COT percentages regardless of duration, 

are presented. Table 10 provides percentages for 

COT ≤1 year and for COT regardless of duration 

for the group with an indicated therapy of ≤1 

year only. Table 57 presents COT percentages by 

ethnicity and non-Hispanic race and by state for 

those among whom therapy ≤1 year was indicated.

TB Disease Site

Miliary disease should be reported as a pulmonary form of TB (Tables 7, 37, and 38). 

Beginning in 2009, miliary disease could not 

be classified as a TB disease site because it is 

a clinical or a radiologic finding and should be 

recorded under Initial Chest Radiograph, Initial 

Chest CT Scan, or Other Chest Imaging Study. 

During 1997–2008, miliary disease was classified as both an extrapulmonary and a pulmonary 

form of TB. In publications before 1997, miliary 

disease was classified as extrapulmonary TB unless pulmonary disease was reported as the major 

TB disease site.

Reporting of HIV Status

Information regarding human immunodeficiency 

virus (HIV) status for persons with TB is displayed in Tables 11 and 50 for those persons 

not dead at diagnosis; Table 11 also lists trend 

data for persons aged 25–44 years. Reporting 

completeness for HIV status has significantly 

improved to 95% of TB patients tested among 

persons aged 25–44 years during 2016; however, 

this variable is still underreported across jurisdictions. Data regarding the HIV-infection status of 

persons reported with TB should be interpreted 

with caution because these data are not representative of all TB patients with HIV infection.

HIV testing is performed after a patient receives counseling and gives informed consent. 

TB patients who are tested anonymously might 

choose not to share HIV testing results with their 
13

health care provider. TB patients managed in 

the private sector can receive confidential HIV 

testing, but results might not be reported to the 

health department’s TB program. Additionally, 

certain factors can influence HIV testing among 

TB patients, including the extent to which testing 

is targeted or routinely offered to specific groups 

(e.g., males aged 25–44 years, injection-drug 

users, or homeless persons) and the availability 

of and access to HIV testing services. These data 

might overrepresent or underrepresent the proportion of TB patients known to be HIV-infected 

in a reporting area.

Primary Occupation for the Past Year

Table 47 reflects the modified 2009 RVCT variable, Primary Occupation Within the Past Year, 

which replaces the Occupation Within Past 24 

Months of TB Diagnosis in previous reports. 

After the 2009 RVCT revision, Multiple Occupation was removed and the Retired and Not Seeking Employment categories were added.

Reason Therapy Was Stopped

Tables 12 and 55 now include a patient’s adverse 

reaction to anti-TB drug therapy as an option 

for the reason therapy was stopped. The 2009 

RVCT revision removed the option of Moved as 

a valid response to the variable Reason Therapy 

Stopped, and this option is therefore not reported 

after 2009. Those cases entered as Moved as 

reason therapy was stopped after 2009 are now 

included in the Unknown category.

Metropolitan Statistical Areas

Tables 60 through 64 present data by metropolitan statistical areas (MSAs) having an estimated 

2016 population of ≥500,000 persons. MSAs 

are defined by the White House Office of Management and Budget (OMB), and the definitions were based on the application of the 2010 

OMB standards for delineating MSAs to Census 

Bureau population estimates for 2012–2013 announced as of July 2015 (https://www.bls.gov/

lau/lausmsa.htm).

The MSA definitions apply to all areas except the 

six New England states; for those states, the New 

England County Metropolitan Areas (NECMAs) 

are used. MSAs are named for a central city in 

the MSA or NECMA, can include multiple cities 

and counties, and can cross state boundaries. For 

example, the TB cases and case rates presented 

for DC in Table 29 include only persons residing 

within DC’s geographic boundaries. However, 

the TB cases and case rates for the Washington, 

DC-MSA (Table 60) include persons residing 

within the multiple counties in the metropolitan 

area, including counties in Maryland, Virginia, 

and West Virginia. Cities or MSAs with incomplete or unavailable data were not included in the 

tables, and certain cities’ or MSAs’ total numbers might be underreported because of missing 

information.

National Tuberculosis Genotyping Service

National Tuberculosis Genotyping Service laboratories primarily use two genotyping methods: 

spoligotyping and MIRU–VNTR (mycobacterial 

interspersed repetitive units–variable number of 

tandem repeats). Both methods require only a 

minor amount of culture material, provide digital 

results, and are relatively quick. Retrospective 

24-locus MIRU–VNTR for older isolates can be 

performed, if requested, and can help in further 

differentiating genotype clusters. All isolates are 

prepared for long-term storage at genotyping 

laboratories or CDC.

Tuberculosis Genotyping Information Management System

In March 2010, the Tuberculosis Genotyping 

Information Management System (TB GIMS) 

was launched by CDC as a secure Internet-based 

system to support ongoing use of TB genotyping 

data in TB control activities. TB GIMS facilitates systematic data collection of TB genotyping 

results, and it integrates genotyping results with 

epidemiologic data collected by NTSS to form a 

national and centralized database. Primary users 

of TB GIMS include TB laboratories that submit 

isolates for genotyping, national CDC-contracted 

genotyping laboratories, state and local TB con-
14

trol programs, and CDC programs that apply this 

information for TB control activities.

Genotyping results from the national genotyping laboratories or CDC are uploaded into TB 

GIMS as they become available. Line-listed data 

from the NTSS are also uploaded into TB GIMS 

weekly. After genotyping results have been 

linked to individual patient surveillance data in 

TB GIMS, the record is considered complete. 

These complete records are essential for the 

majority of the applications of TB genotyping, 

including all reports and maps as well as for 

using the outbreak detection system to identify 

potential chains of transmission and outbreaks. 

Twenty-four system updates have occurred for 

adding new reports, data management functions, 

and other tools since TB GIMS was released 

in March 2010. As of July 2017, a total of 579 

local, state, and federal users have accessed the 

system.

Genotype Clustering

A genotype cluster comprises two or more cases 

in a jurisdiction during a specified period having M. tuberculosis isolates that share matching 

genotypes. The jurisdiction and period used vary 

on the basis of the specific application. Cases 

that are part of the same genotype cluster are 

likely to be related by TB transmission in some 

way; however, the cases might not be directly 

related (i.e., one person did not necessarily give 

TB to another person in the cluster) or recently 

related (i.e., both persons might have contracted 

TB from the same person, but the exposure 

might have happened years ago). In TB GIMS, 

clustering is defined as ≥2 cases with matching 

genotypes (spoligotype and 24-locus MIRU-VNTR) in a single county within a 3-year period.

Mycobacterium bovis

For culture-confirmed TB cases that have been 

genotyped, Mycobacterium bovis can be defined 

primarily on the basis of spoligotyping results. 

The genotype-based definition for M. bovis

required either (1) the absence of spoligotyping 

spacers 3, 9, 16, and 39–43; the presence of ≥1 

of the spacers 29–32; and the presence of ≥1 of 

the spacers 33–36; or (2) the absence of spacers 

3, 9, 16, and 39–43 and ≥2 copies of the repeated 

sequence at MIRU locus 24; or (3) determination based on microbiologic expertise. Data 

reported for 2004–2016 exclude cases of bacillus 

Calmette-Guérin M. bovis, which were defined 

as spoligotype 676773777777600 with x, y, or 

z in the second MIRU position. Although cases 

of bacillus Calmette-Guérin M. bovis (defined as 

spoligotype 676773777777600 with x, y, or z in 

the second MIRU position) were reported during 

2004–2016, they are excluded from this report.

Recent Transmission

Estimates are based on a plausible-source case 

method that is described in detail elsewhere.3

Briefly, a given case is designated as attributed 

to recent transmission if a plausible source case 

with the following five characteristics can be 

identified in the national surveillance data: the 

same M. tuberculosis GENType, an infectious 

form of TB disease, patient's residential location 

within 10 miles, patient’s age ≥10 years, and a 

diagnosis within the 2 years before the given 

case. These criteria were field-validated using 

local epidemiologic assessments of whether 

1,188 cases in three states were actually due to 

recent transmission that was attributed to source 

cases reported during 1996–2000. Any given 

case with a plausible source case identified is 

included regardless of cluster size. Among cases 

attributed to overall recent transmission, a given 

case can also be attributed to extensive recent 

transmission if at least five other cases could 

be identified in a plausible transmission chain 

within 3 years prior to the given case.

3

France AM, Grant J, Kammerer JS, Navin TR. A 

field-validated approach using surveillance and 

genotyping data to estimate tuberculosis attributable to recent transmission in the United States. 

Am J Epidemiol 2015; 182: 799-807.