DOI: 10.3886/icpsr35064
title: Trends in Undiagnosed Chlamydia Prevalence in Baltimore, 1997-1998 and 2006-2009
title: Archival Version

description: The 1997-1998 Baltimore STD and Behavior Survey (BSBS) and the 2006-2009 Monitoring STIs Survey Program (MSSP) collected biospecimens from adults ages 18 to 35 in Baltimore to estimate trends in undiagnosed chlamydial infection. The survey recruited a population sample of young adults to participate in an in-person survey of sexual and other sensitive behaviors and STD history. BSBS data collection was conducted over the period of January, 1997 through September, 1998. Respondents also provided a urine sample. The MSSP collected telephone survey data and eligible respondents mailed in specimens for testing. The biospecimens allowed for continuous monitoring of three STIs -- gonorrhea, chlamydial infection, and trichomoniasis. The data collection contains variables about infection symptoms, use of antibiotics, sexual activity and behavior, domestic violence, drug use and whether respondents are positive for chlamydia. Demographic information includes gender, age, education, marital status, race, and employment status.
description: To provide a more accurate understanding of the hidden epidemics of untreated infection with N. gonorrhoeae and C. trachomatis.
description: Please see the Original P.I. Documentation in the ICPSR User Guide for more information about the study design.
description: The data are not weighted; however, this collection contains the weight variable BIOSPECIMEN_WT, which should be used in analysis. Two sets of BSBS sample weights were constructed to project (1) survey questionnaire results and (2) urine assay results to the reference population of Baltimore. The general approach to BSBS weight calculation involved the following steps: (1) compute housing unit level weights for the base sample, the black male supplement, and white-high STD supplement \x{2014} including adjustments for exceptions from planned size measures and planned within-property sample sizes; (2) add original identification number (based on sample from which originally drawn) to each sample record and compute rework sample weight adjustment; (3) identify base sample records that would also have been eligible for the stratum 1 high-STD sample; (4) impute any data essential for weight calculation or adjustment, compute multiplicity indicators and adjustment factors, compute rework sample weight factor, and derive design-based weights at the person level; (5) post-stratify the design-based weights to match external controls by race, gender, and age and then normalize weights to sum to 1 within mode; (6) trim extreme design weights, re-stratify, and re-normalize; (7) run extensive check tabulations to confirm general correctness of approach. Two sets of MSSP sample weights were constructed to adjust for the unequal probabilities of selection based on our stratified sample design and survey nonresponse. Initial weights were developed reflecting the inverse probability of selection within each stratum with adjustments for the differing probabilities of selection within households, the number of landline telephones within the household, and survey nonresponse. A post-stratification adjustment was applied to align the sample distribution with the 2006-2009 United States Census estimates of the Baltimore City population by age, gender, and race/ethnicity [26]. A second set of weights was constructed to compensate for additional differences in the provision of a biospecimen for STI testing among respondents who completed the survey interview. Analysis of the combined BSBS and MSSP chlamydia data should use the weight variable \"biospecimen_wt\" which merges weights from the two surveys and should be done in conjunction with the composite strata variable (\"strata\"). Stata users can use the SYVSET command: svyset [pweight=biospecimen_wt], strata (strata) singleunit (scaled).
description: Response Rates: BSBS:85.7 percent screened.82.8 percent interviewed. 79.5 percent provided a urine specimen adequate for testing; 16.3 percent refused to provide a urine specimen and 4.1 percent were not tested because of inadequate urine volume, interviewer error, or other logistical problems. MSSP: 69.5 percent were screened, 58.7 percent interviewed, 72.8 percent mailed in specimens for testing.
description: The sample for the Baltimore STD and Behavior Survey was drawn from households residing within the municipal boundaries of the city of Baltimore (1998 population: 645,664). Households were selected using a stratified probability sampling design that selected residences from the Baltimore Real Estate Property Registry. This registry includes all properties -- both taxable and tax-exempt -- within the city of Baltimore. Two sample strata were disproportionately sampled to ensure adequate representation of (1) young black men and (2) young adults living in predominantly white US Census tracts with elevated levels of STDs (based on Baltimore City Health Department [BCHD] STD surveillance statistics). Operationally, these two strata comprised (1) households with an age-eligible man drawn from census tracts with 95 percent to 100 percent black residents according to the 1990 US Census; and (2) adults aged 18 to 35 years residing in 13 census tracts that had the highest rates of reported gonococcal infection among tracts with 0 percent to 9 percent black residents. A third crosscutting sample stratum was created to accommodate the refielding of a 50 percent random subsample of cases for which our quality control procedures could not verify the integrity of the interview data. This sample design oversampled segments of the population that are known to have higher rates of STDs (i.e., young black men and whites living in US Census tracts with high rates of reported STDs). BSBS prevalence estimation used sampling weights to adjust for the unequal probabilities of selection across sample strata. The MSSP collected telephone survey data and biospecimens for continuous monitoring of three STIs -- gonorrhea, chlamydial infection, and trichomoniasis among probability samples of adolescents and young adults residing in Baltimore, MD. Recruitment for the MSSP began in September 2006 and ended in June 2009. A stratified, list-assisted, probability sampling design was used to maximize sample efficiency in identifying our target population of English-speaking males and females between 15 and 35 years of age residing in Baltimore households with landline telephones. The probability sample included four strata. The first three strata were sampled using commercially-available, regularly updated information on Baltimore households.
description: Datasets: DS1: Trends in Undiagnosed Chlamydia Prevalence in Baltimore, 1997-1998 and 2006-2009
description: Population of Baltimore MD, ages 18 to 35 years. Smallest Geographic Unit: city
description: audio computer-assisted self interview (ACASI); face-to-face interview; telephone audio computer-assisted self interview (TACASI); telephone interviewThis collection is related to ICPSR #35066 "Undiagnosed Trichomoniasis Infection in the Population of Baltimore, MD: Data from the 2006 - 2009 Monitoring STIs Survey Program".