Epidemiology of undiagnosed trichomoniasis in a probability sample of urban young adults.

T. vaginalis infection (trichomoniasis) is the most common curable sexually transmitted infection (STI) in the U.S. It is associated with increased HIV risk and adverse pregnancy outcomes. Trichomoniasis surveillance data do not exist for either national or local populations. The Monitoring STIs Survey Program (MSSP) collected survey data and specimens which were tested using nucleic acid amplification tests to monitor trichomoniasis and other STIs in 2006-09 among a probability sample of young adults (N = 2,936) in Baltimore, Maryland--an urban area with high rates of reported STIs. The estimated prevalence of trichomoniasis was 7.5% (95% CI 6.3, 9.1) in the overall population and 16.1% (95% CI 13.0, 19.8) among Black women. The overwhelming majority of infected men (98.5%) and women (73.3%) were asymptomatic. Infections were more common in both women (OR = 3.6, 95% CI 1.6, 8.2) and men (OR = 9.0, 95% CI 1.8, 44.3) with concurrent chlamydial infection. Trichomoniasis did not vary significantly by age for either men or women. Women with two or more partners in the past year and women with a history of personal or partner incarceration were more likely to have an infection. Overall, these results suggest that routine T vaginalis screening in populations at elevated risk of infection should be considered.

Gender-based screening for chlamydial infection and divergent infection trends in men and women.

OBJECTIVES: To assess the potential impact of chlamydial screening policy that recommends routine screening of women but not men. METHODS: Population surveys of probability samples of Baltimore adults aged 18 to 35 years in 1997-1998 and 2006-2009 collected biospecimens to estimate trends in undiagnosed chlamydial infection. Survey estimates are compared to surveillance data on diagnosed chlamydial infections reported to the Health Department. RESULTS: Prevalence of undiagnosed chlamydial infection among men increased from 1.6% to 4.0%, but it declined from 4.3% to 3.1% among women (p = 0.028 for test of interaction). The annual (average) number of diagnosed infections was substantially higher among women than men in both time periods and increased among both men and women. Undiagnosed infection prevalence was substantially higher among black than non-black adults (4.0% vs 1.2%, p = 0.042 in 1997-98 and 5.5% vs 0.7%, p<0.001 in 2006-09). CONCLUSION: Divergent trends in undiagnosed chlamydial infection by gender parallel divergent screening recommendations that encourage chlamydial testing for women but not for men.

'What's in the NIDDK CDR?'--public query tools for the NIDDK central data repository.

The National Institute of Diabetes and Digestive Disease (NIDDK) Central Data Repository (CDR) is a web-enabled resource available to researchers and the general public. The CDR warehouses clinical data and study documentation from NIDDK funded research, including such landmark studies as The Diabetes Control and Complications Trial (DCCT, 1983-93) and the Epidemiology of Diabetes Interventions and Complications (EDIC, 1994-present) follow-up study which has been ongoing for more than 20 years. The CDR also houses data from over 7 million biospecimens representing 2 million subjects. To help users explore the vast amount of data stored in the NIDDK CDR, we developed a suite of search mechanisms called the public query tools (PQTs). Five individual tools are available to search data from multiple perspectives: study search, basic search, ontology search, variable summary and sample by condition. PQT enables users to search for information across studies. Users can search for data such as number of subjects, types of biospecimens and disease outcome variables without prior knowledge of the individual studies. This suite of tools will increase the use and maximize the value of the NIDDK data and biospecimen repositories as important resources for the research community. Database URL: https://www.niddkrepository.org/niddk/home.do.

Incarceration, high-risk sexual partnerships and sexually transmitted infections in an urban population.

OBJECTIVES: The authors examined the associations between personal and partner incarceration, high-risk sexual partnerships and biologically confirmed sexually transmitted infection (STI) in a US urban population. METHODS: Data from a probability survey of young adults 15-35 years of age in Baltimore, Maryland, USA, were analysed to assess the prevalence of personal and partner incarceration and its association with several measures of high-risk sexual partnerships including multiple partners, partner concurrency and current STI. RESULTS: A history of incarceration was common (24.1% among men and 11.3% among women). Among women with an incarcerated partner in the past year (15.3%), the risk of current STI was significantly increased (adjusted prevalence ratio=2.3, 95% CI 1.5 to 3.5). Multiple partners (5+) in the past year and partner concurrency were disproportionately high among men and women who had been incarcerated or who had sexual partner(s) or who had recently been incarcerated. These associations remained robust independent of personal socio-demographic factors and illicit drug use. CONCLUSIONS: Incarceration may contribute to STI risk by influencing engagement in high-risk behaviours and by influencing contact with partners who engage in risky behaviours and who hence have elevated risk of infection.

The NIDDK Central Repository at 8 years--ambition, revision, use and impact.

The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) Central Repository makes data and biospecimens from NIDDK-funded research available to the broader scientific community. It thereby facilitates: the testing of new hypotheses without new data or biospecimen collection; pooling data across several studies to increase statistical power; and informative genetic analyses using the Repository's well-curated phenotypic data. This article describes the initial database plan for the Repository and its revision using a simpler model. Among the lessons learned were the trade-offs between the complexity of a database design and the costs in time and money of implementation; the importance of integrating consent documents into the basic design; the crucial need for linkage files that associate biospecimen IDs with the masked subject IDs used in deposited data sets; and the importance of standardized procedures to test the integrity data sets prior to distribution. The Repository is currently tracking 111 ongoing NIDDK-funded studies many of which include genotype data, and it houses over 5 million biospecimens of more than 25 types including serum, plasma, stool, urine, DNA, red blood cells, buffy coat and tissue. Repository resources have supported a range of biochemical, clinical, statistical and genetic research (188 external requests for clinical data and 31 for biospecimens have been approved or are pending). Genetic research has included GWAS, validation studies, development of methods to improve statistical power of GWAS and testing of new statistical methods for genetic research. We anticipate that the future impact of the Repository's resources on biomedical research will be enhanced by (i) cross-listing of Repository biospecimens in additional searchable databases and biobank catalogs; (ii) ongoing deployment of new applications for querying the contents of the Repository; and (iii) increased harmonization of procedures, data collection strategies, questionnaires etc. across both research studies and within the vocabularies used by different repositories.

Chlamydia trachomatis infection among 15- to 35-year-olds in Baltimore, MD.

BACKGROUND: Chlamydia trachomatis (Ct) is the most frequently reported infectious disease in the United States. This article reports population and subpopulation prevalence estimates of Ct and correlates of infection among 15- to 35-year-olds in Baltimore, MD. METHODS: The Monitoring STIs Survey Program (MSSP) monitored sexually transmitted infection (STI) prevalence among probability samples of residents of Baltimore, a city with high STI rates. MSSP respondents completed telephone audio computer-assisted self-interviews and provided biospecimens for STI testing. RESULTS: Among 2120 Baltimore residents aged 15 to 35 years, the estimated prevalence of chlamydia was 3.9% (95% confidence interval [CI]: 2.8, 5.0). Prevalence was 5.8% (95% CI: 4.1, 7.6) among black MSSP respondents versus 0.7% (95% CI: 0.0, 1.4) among nonblack respondents; all but 4 infections detected were among black respondents. Sexual behaviors and other factors associated with infection were far more prevalent among black than nonblack Baltimore residents. Racial disparities persisted after adjustment for sociodemographic, behavioral, and health factors. CONCLUSION: The MSSP highlights a higher Ct prevalence among young people in Baltimore than in the United States overall, with notable racial disparities in infection and associated risk behaviors. Public health efforts are needed to improve the diagnosis and treatment of asymptomatic infections in this population.

Improving epidemiological surveys of sexual behaviour conducted by telephone.

BACKGROUND: This study assesses the impact of Telephone Audio Computer-Assisted Self-Interviewing (T-ACASI) on the reporting of sensitive (mainly heterosexual) behaviours. METHODS: A randomized experiment was embedded in a telephone survey that drew probability samples of the populations of the USA (N = 1543) and Baltimore city (N = 744). Respondents were randomly assigned to have questions asked either by a T-ACASI computer or by a human telephone interviewer. RESULTS: Compared with interviewer-administered telephone surveys, T-ACASI obtained more frequent reporting of a range of mainly heterosexual behaviours that were presumed to be sensitive, including recency of anal sex [adjusted odds ratio (A-OR) = 2.00, P < 0.001), sex during menstrual period (A-OR = 1.49, P < 0.001), giving oral sex (A-OR = 1.40, P = 0.001) and receiving oral sex (A-OR = 1.36, P = 0.002), and sexual difficulties for the respondent (A-OR = 1.45, P = 0.034) and their main sex partner (A-OR = 1.48, P = 0.0). T-ACASI also obtained less frequent reporting that respondent had a 'main sex partner' (A-OR = 0.56, P = 0.011) and discussed contraception prior to first sex with that sex partner (A-OR = 0.82, P = 0.094). For both males and females, T-ACASI obtained more frequent reports of first vaginal sex occurring at early ages (before ages 12 through 15). 'For males only', T-ACASI also elicited more frequent reports that first vaginal sex had 'not' occurred at later ages (i.e. by ages 20 through 24). CONCLUSION: T-ACASI increases the likelihood that survey respondents will report sensitive heterosexual behaviours.

Impact of T-ACASI on Survey Measurements of Subjective Phenomena.

Numerous studies have shown that audio-computer-assisted self-interviewing (audio-CASI) and telephone audio-CASI (T-ACASI) technologies yield increased reporting of sensitive and stigmatized objective phenomena such as sexual and drug use behaviors. Little attention has been given, however, to the impact of these technologies on the measurement of subjective phenomena (attitudes, opinions, feelings, etc.). This article reports results for the seven subjective measurements included in the National STD and Behavior Measurement Experiment (NSBME). NSBME drew probability samples of USA and Baltimore adults (Ns = 1,543 and 744, respectively) and randomized these respondents to be interviewed by T-ACASI or telephone interviewer-administered questioning (T-IAQ). Response distributions for all subjective measurements obtained by T-ACASI diverge from those obtained by human telephone interviewers. For six of our seven ordinal-scaled measurements, this divergence involved shifting responses directionally along the ordinal scale, as opposed to a nondirectional redistribution among response categories. When interviewed by T-ACASI, respondents were more supportive of traditional gender roles and corporal punishment, less supportive of integrated neighborhoods and same-gender sex, and more likely to agree that occasional marijuana use is harmless and to describe themselves as attractive. The majority of these results suggest that telephone survey respondents may provide more "tolerant" and "socially liberal" responses to human interviewers than to a T-ACASI computer. Similarly, although the evidence is not entirely consistent, the impact of T-ACASI appears to increase with the social vulnerability of the population surveyed.

T-ACASI reduces bias in STD measurements: the National STD and Behavior Measurement Experiment.

BACKGROUND: Although telephone surveys provide an economical method for assessing patterns of diagnosed sexually transmitted diseases (STDs) and STD-related behaviors in populations, the requirement that respondents report such information to human telephone interviewers introduces an opportunity for substantial reporting bias. Telephone computer-assisted self-interviewing (T-ACASI) surveys substitute a computer for human interviewers when asking sensitive questions. METHODS: A randomized experiment was embedded in a telephone survey that drew probability samples of the populations of the United States (N = 1543) and Baltimore city (N = 744). Respondents were randomly assigned to have sensitive questions asked either by a T-ACASI computer or by a human telephone interviewer. RESULTS: Respondents interviewed by a T-ACASI computer were more likely to report STD symptoms [dysuria, genital sores, genital discharge, and genital warts; adjusted odds ratios (ORs) = 1.5-2.8] and a diagnosis of gonococcal or chlamydial infection during the past year (adjusted ORs = 3.6 and 6.1). T-ACASI respondents with a main sex partner in the past year were more likely to report that their partner has had an STD (adjusted OR = 2.4). For some measurements, the impact of T-ACASI was strongest among younger and less-educated respondents. When sampling weights were applied to project National STD and Behavior Measurement Experiment results to the populations of the United States and Baltimore, we found that reliance on data obtained by human interviewers would underestimate the annual incidence of chlamydial and gonococcal infections in these populations by factors of 2.4 to 9.7. CONCLUSIONS: Compared with human telephone interviewers, T-ACASI surveys obtain increased reporting of STD symptoms, infections, and STD-related behaviors.

Do asthma medication beliefs mediate the relationship between minority status and adherence to therapy?

Minority status has been associated with lower asthma medication adherence. We evaluated whether medication beliefs mediated this association. 86 adults with asthma on inhaled corticosteroid therapy completed surveys regarding selected beliefs about asthma medications. Medication adherence for 1 month was electronically measured. Mean daily adherence was lower in minority patients than in Caucasians (p < .001). Multiple negative asthma medication beliefs were associated with lower adherence (p's < .05). Minorities had increased adjusted odds of having a high negative medication beliefs score. Finally, a bootstrapped estimate demonstrated a mediating effect by negative asthma beliefs on the minority status-adherence association (-.073 [95% CI: -.16, -.01]).

SAME-GENDER SEX IN THE UNITED STATES IMPACT OF T-ACASI ON PREVALENCE ESTIMATES.

Well-conducted telephone surveys provide an economical means of estimating the prevalence of sexual and reproductive behaviors in a population. There is, however, a nontrivial potential for bias since respondents must report sensitive information to a human interviewer. The National STD and Behavior Measurement Experiment (NSBME) evaluates a new survey technology-telephone audio computer-assisted self-interviewing (T-ACASI)-that eliminates this requirement. The NSBME embedded a randomized experiment in a survey of probability samples of 1,543 U.S. and 744 Baltimore adults ages 18 to 45. Compared with NSBME respondents interviewed by human interviewers, respondents interviewed by T-ACASI were 1.5 to 1.6 times more likely to report same-gender sexual attraction, experience, and genital contact. The impact of T-ACASI was more pronounced (odds ratio = 2.5) for residents of locales that have historically been less tolerant of same-gender sexual behaviors and for respondents in households with children (odds ratio = 3.0).

Reducing bias in telephone survey estimates of the prevalence of drug use: a randomized trial of telephone audio-CASI.

AIM: To assess the impact of telephone audio computer-assisted self-interviewing (T-ACASI) on reporting of alcohol use, alcohol problems and illicit drug use in telephone surveys of the general population. Prior research suggests that illicit drug use is underreported in traditional, interviewer-administered, telephone surveys. DESIGN: Randomized experiment embedded in telephone survey of probability samples of populations of USA and Baltimore, MD. Survey respondents were randomly assigned to be interviewed either by human telephone interviewers or by T-ACASI after household screening, recruitment, and informed consent procedures were completed. SETTING: Respondents were interviewed by telephone in their homes. PARTICIPANTS: Probability samples of 1543 English-speaking adults ages 18-45 residing in telephone-accessible households in USA and 744 similarly defined adults residing in Baltimore, MD, USA. MEASUREMENTS: Nine questions on alcohol, marijuana, cocaine, and injection drug use adapted from 1994 NHSDA and four CAGE questions on alcohol problems. Crude odds ratios and odds ratios controlling for demographic factors calculated to test for differences between responses obtained by T-ACASI and human interviewers. FINDINGS: T-ACASI had mixed effects on reporting of alcohol use, but it did increase reporting of one of four CAGE alcohol problems: feeling guilty about drinking (23.0% in T-ACASI vs. 17.6% in T-IAQ, OR = 1.4, P < 0.01). T-ACASI also obtained significantly more frequent reporting of marijuana, cocaine, and injection drug use. The impact of T-ACASI was most pronounced for reporting of recent use of 'harder' drugs. Thus T-ACASI respondents were more likely to report marijuana use in the past month (10.0% vs. 5.7%, crude OR = 1.9, P < 0.001), cocaine use in the past month (2.1% vs. 0.7%, crude 3.2, P < 0.001) and injection drug use in the past five years (1.6% vs. 0.3%, crude OR = 4.8, P < 0.01). CONCLUSIONS: Telephone survey respondents were more likely to report illicit drug use and one alcohol problem when interviewed by T-ACASI rather than by human telephone interviews.

Polymerase chain reaction detection of Y chromosome sequences in vaginal fluid: preliminary studies of a potential biomarker for sexual behavior.

BACKGROUND: Self-reported measures of sexual behavior are subject to nontrivial reporting biases. OBJECTIVE: The objective of this study was to develop a behavioral biomarker of recent sexual activity among females that is inexpensive, easily administered, and can be used in low sexually transmitted disease prevalence populations. METHODS: We developed a polymerase chain reaction (PCR) assay to detect Y chromosome (Yc) fragments. The Yc primers were developed against a 200-basepair (bp) microsatellite repeat sequence, which is unique to the male genome. A standard PCR technique was used. Assay sensitivity was determined quantitatively using donated semen samples. To assess longevity of detectability, we recruited female subjects in monogamous relationships. Seventeen subjects had unprotected intercourse followed by 3 weeks of abstinence from vaginal intercourse. Self-administered vaginal swabs (SAVS) were collected every other day. In addition to the swabs, subjects kept daily sexual diaries. Swabs were processed by semiquantitative PCR, and Yc decay curves were determined for each subject. The half-life of Yc in vaginal fluid was calculated on the collection of individual decay curves by a random-effects regression model approach. RESULTS: The sensitivity of our Yc-PCR assay was determined to be 5 copies of Yc. In the longevity studies, Yc was detectable in SAVS up to 15 postcoital days (PCD). Mean Yc DNA concentration in SAVS eluate followed an exponential decay pattern for each subject. Mean concentrations were 66.7 ng/mL at PCD-1, 20.6 ng/mL at PCD-7, and 4.5 ng/mL at PCD-15. The estimated half-life for Yc clearance was 3.83 days. CONCLUSION: The swab-based Yc-DNA PCR assay can detect coitus in women for a 2-week retrospective period. This can be used to validate sexual behavior-reporting and condom use in women and promises to be a useful tool in sexual behavior research.

SAME-GENDER SEX AMONG U.S. ADULTS: TRENDS ACROSS THE TWENTIETH CENTURY AND DURING THE 1990s.

Trends in reporting of same-gender sex are assessed using data from the 1988-2002 General Social Surveys (Ns = 9,487 males and 12,336 females). Analyses indicate that the reported prevalence of female-female sexual contact increased substantially and monotonically across twentieth-century birth cohorts, rising from 1.6 percent (Standard error [SE] = 0.60) for the cohort of U.S. women born prior to 1920 to 6.9 percent (SE = 0.81) for women born in 1970 and afterward. Increases in the reported prevalence of female-female contacts also occurred within the 1990s. These trends persist when statistical controls are introduced for changes in attitudes toward same-gender sexual behavior. No parallel trend is observed in the reporting of male-male sexual contacts during adulthood, although the proportion of U.S. men reporting such contacts in the past year and in the past five years increased during the 1990s.

Audio-computerized self-interviewing versus face-to-face interviewing for research data collection at drug abuse treatment programs.

AIMS: To assess audio computer-assisted self-interviewing (A-CASI) as a mode of data collection with injecting drug users (IDUs) entering two drug treatment programs in New York City. A-CASI has been found to increase reporting of sensitive items among a variety of population subgroups. DESIGN: A field test of A-CASI data collection conducted within an ongoing cross-sectional study of drug use and HIV risk behaviors among IDUs entering drug treatment. Participants were assigned without bias to either a computer-assisted interviewer-administered personal interview (CAPI) or to a mixed CAPI/A-CASI interview. In the latter, 'sensitive' portions (dealing with stigmatized behavior) of the questionnaire were self-administered through A-CASI, while the remaining portions were interviewer-administered. SETTING: The Detoxification Program and the Methadone Maintenance Treatment Program (MMTP) at Beth Israel Medical Center in New York City. PARTICIPANTS: Seven hundred and eighty-three IDUs entering drug treatment. MEASUREMENTS: Odds ratios and adjusted odds ratios (controlling for demographic differences) for comparison of A-CASI versus CAPI responses on 111 sensitive questions. FINDINGS: Twenty-three statistically significant differences (each at P < 0.05), all in the direction of more reporting of the behaviors by the A-CASI group. Forty-one per cent of A-CASI participants said they would prefer any subsequent interviews to be fully A-CASI and 46% said they would prefer the mixed CAPI/A-CASI mode. CONCLUSIONS: A-CASI was associated with greater reporting of potentially stigmatized drug, sex and HIV risk behaviors on a moderate number of questions. Moreover, a large majority of participants who used A-CASI would like to be assigned to this method of data collection in future interviews.

Does Telephone Audio Computer-Assisted Self-Interviewing Improve the Accuracy of Prevalence Estimates of Youth Smoking? Evidence from the UMass Tobacco Study.

Despite their advantage for obtaining representative samples of adolescents, telephone surveys have been regarded as inferior for collecting data on youth tobacco use because they yield lower estimates than school-based self-administered surveys. Although no gold standard for smoking estimates exists, the lower estimates in telephone surveys have been attributed to underreporting due to youths' concern about parents or others overhearing their responses. Telephone audio computer-assisted self-interviewing (T-ACASI) is a cost-effective method for obtaining a representative sample of youths and provides increased privacy for the respondent. We hypothesized that using T-ACASI would encourage youths to more fully report smoking behavior compared to traditional interviewer-administered telephone methods. Our analysis further assessed whether respondent age, gender, race/ethnicity, and parental attitude toward smoking moderated the relationship between survey mode and smoking reports. Using data from a statewide tobacco use survey that randomly assigned youth respondents to either T-ACASI or interviewer-administered mode, we found youths were more likely to report smoking behaviors in T-ACASI mode and that this was especially true for girls, particularly those who believed their parents would disapprove strongly of their smoking. Findings suggest that traditional telephone surveys may underestimate smoking prevalence in most girls by a factor of two, and that a technique for insuring privacy for these respondents is an important component of effective telephone survey methodology.

NAAT-identified and self-reported gonorrhea and chlamydial infections: different at-risk population subgroups?

BACKGROUND: Information on the characteristics and behaviors of persons at high risk for gonorrhea and chlamydial infection has typically been derived from studies of sexually transmitted disease (STD) clinic populations. The Baltimore STD and Behavior Survey (BSBS) used urine-based nucleic acid amplification testing (NAAT) to assess the prevalence and behavioral correlates of gonorrhea and chlamydial infection in a population-based cross-sectional survey of adults in Baltimore, Maryland. GOAL: The goal of this study was to examine the demographic characteristics and behavioral markers of gonorrhea and chlamydial infection as reported by adults with a self-reported history of gonorrhea and chlamydial infection and to compare these to the characteristics and behaviors of individuals with current NAAT-identified gonorrhea and/or chlamydial infection. STUDY DESIGN: A probability sample of adults aged 18 to 35 years residing in Baltimore was evaluated with collection of urine specimens and administration of a health and behavior survey. Data and specimens were collected between January 1997 and September 1998. RESULTS: Respondents with NAAT-detected gonorrhea and/or chlamydial infection (7.9%) did not report a history of high-risk behaviors or more recent occurrences of those behaviors, and the majority were asymptomatic. However, adults in our study who self-reported a history of infection (26.0%) were more likely than those with no history of infection to report multiple partners, paid sex, partners with prior STDs, and STD symptoms-a pattern consistent with findings described in previous clinic-based reports. CONCLUSION: The risk profile generated from studies of clinic populations, with a focus on symptomatic disease, may not characterize the broader population with current, untreated, largely asymptomatic infection.

Risk behaviors, medical care, and chlamydial infection among young men in the United States.

OBJECTIVES: This study assessed factors related to chlamydial infection among young men in the United States. METHODS: Data were from interviews of nationally representative samples of 470 men aged 18 to 19 years (teenagers) and 995 men aged 22 to 26 years (young adults) and from urine specimens tested by means of polymerase chain reaction. RESULTS: Although a majority of the men reported occasional unprotected intercourse, only a minority perceived themselves to be at risk for contracting a sexually transmitted disease (STD). Chlamydial infection was detected in 3.1% of the teenagers and 4.5% of the young adults. A minority of those infected had symptoms or had been tested for STDs; very few had been diagnosed with STDs. CONCLUSIONS: Chlamydial infection is common but usually asymptomatic and undiagnosed. Primary and secondary prevention efforts should be increased, particularly among young adult men.

Untreated gonococcal and chlamydial infection in a probability sample of adults.

CONTEXT: The prevalence and distribution of gonococcal and chlamydial infections in the general population are poorly understood. Development of nucleic acid amplification tests, such as the ligase chain reaction assay, provides new opportunities to estimate the prevalence of untreated infections in the population. OBJECTIVE: To estimate the overall prevalence of untreated gonococcal and chlamydial infections and to describe patterns of infection within specific demographic subgroups of the young adult population in Baltimore, Md. DESIGN AND SETTING: Cross-sectional behavioral survey based on a probability sample of Baltimore households with collection of urine specimens between January 1997 and September 1998. PARTICIPANTS: A total of 728 adults aged 18 to 35 years completed the interview portion of the study, and 579 of these respondents also provided a urine specimen adequate for testing. MAIN OUTCOME MEASURE: Prevalence of untreated infection, as measured by the percentage of specimens testing positive for gonococcal and chlamydial infection by ligase chain reaction, weighted to reflect variations in probabilities of sample selection from the population. Alternate estimates of the prevalence of recent treated infection were derived from clinically diagnosed cases reported to the Baltimore City Health Department and by diagnoses reported by participants in the survey. RESULTS: An estimated 5.3% (SE, 1.4%) of the population aged 18 to 35 years has an untreated gonococcal infection, and 3.0% (SE, 0.8%) is estimated to have an untreated chlamydial infection. While 7.9% (SE, 1.6%) of the population is estimated to have either an untreated gonococcal or chlamydial infection, estimated prevalence is substantially higher among black women (15.0%; SE, 3.7%). Few participants with untreated infections reported dysuria or discharge during the 6 months preceding testing. The estimated number of untreated gonococcal infections in the population (9241; SE, 2441) substantially exceeds both the number of such infections diagnosed among Baltimore adults aged 18 to 35 years and reported to the Baltimore City Health Department during 1998 (4566), and the estimated number of diagnoses derived using participants' reports for the 12 months prior to the survey (4708 [SE, 1918] to 5231 [SE, 2092]). The estimated number of untreated chlamydial infections (5231; SE, 1395) is also greater than the number of cases reported to the health department in 1998 (3664) but is slightly less than the estimated number of diagnoses derived using participants' reports of chlamydial infections diagnosed during the 12 months prior to the survey (5580 [SE, 1918] to 6975 [SE, 2441]). CONCLUSION: In 1997-1998, the estimated number of undiagnosed gonococcal and chlamydial infections prevalent in the population of Baltimore adults aged 18 to 35 years approached or exceeded the number of infections that were diagnosed and treated annually.