Group testing, where individual specimens are composited into groups to test for the presence of a disease (or other binary characteristic), is a procedure commonly used to reduce the costs of screening a large number of individuals. Group testing data are unique in that only group responses may be available, but inferences are needed at the individual level. A further methodological challenge arises when individuals are tested in groups for multiple diseases simultaneously, because unobserved individual disease statuses are likely correlated. In this paper, we propose new regression techniques for multiple-disease group testing data. We develop an expectation-solution based algorithm that provides consistent parameter estimates and natural large-sample inference procedures. We apply our proposed methodology to chlamydia and gonorrhea screening data collected in Nebraska as part of the Infertility Prevention Project and to prenatal infectious disease screening data from Kenya. Copyright © 2013 John Wiley & Sons, Ltd.

OBJECTIVE:

To describe the trends in chlamydia positivity among New Orleans high school students tested in a schoolwide screening between 1996 and 2005, and to determine factors associated with chlamydia positivity among students during the 10-year period.

METHODS:

Between school years 1995-1996 and 2004-2005, students in New Orleans public high schools were tested for chlamydia using nucleic acid amplification tests (NAAT) in urine specimens (LCx assay until 1999-2000; BD assay from 2000-2001 to 2004-2005). For each year, we calculated chlamydia positivity by dividing the number of students testing positive by the total number of students tested. Data were analyzed separately by gender. Logistic regressions were performed to determine independent predictors of chlamydia positivity during the 10-year period.

RESULTS:

Between 1996 and 2005, the average chlamydia positivity was 7.0% (95% confidence interval 6.6-7.4) in boys and 13.1% (95% confidence interval 12.6-13.7) in girls (P < .001). Chlamydia detection increased with the switch from LCx to BD assay. In multivariate analyses, chlamydia positivity among boys and girls was significantly associated with age, black race, and gonorrhea coinfection. Additionally, positivity was significantly different by school year among boys (P = .03) and by NAAT used among girls (P = .008).

CONCLUSIONS:

The trends in chlamydia positivity observed between 1996 and 2005 more likely reflected a high and stable prevalence of chlamydia in the New Orleans school-age adolescent population. Any benefit of screening on individuals tested was likely to be mitigated by participants' uninterrupted social interactions with the dynamic forces that sustain the sexual transmission of chlamydia in the population.

Introduction:Trichomonas vaginalis is a common sexually transmitted infection (STI) causing vaginitis. Microscopy has poor sensitivity but is used for diagnosis of trichomoniasis in resource-poor settings. We aimed to provide a more reliable diagnosis of trichomoniasis by investigating an association with leukorrhea.Materials and

Methods:

Women presenting for evaluation of vaginal discharge, STI exposure, or preventative gynecologic examination were evaluated for Trichomonas infection. Vaginal pH and microscopy was performed by the provider, who recorded the number of polymorphonuclear leukocytes (PMNLs) per epithelial cell and the presence of clue cells, yeast, and/or motile trichomonads. Leukorrhea was defined as greater than one PMNL per epithelial cell. Culture and a nucleic acid amplification test (NAAT) were used to detect T. vaginalis. Patients were evaluated for Chlamydia trachomatis and Neisseria gonorrhoeae using NAATs and bacterial vaginosis using Gram stains.

Results:

294 women were enrolled and 16% were found to have Trichomonas (46/294). Trichomonas infection was more common in parous non-Hispanic, black women who reported low rates of contraceptive use (33% vs. 17%, p-value =0.02) and a STI history (85% vs. 55%, p-value=0.002). These women were more likely to report vaginal discharge (76% vs. 59%, p-value =0.02), have an elevated vaginal pH (87% vs. 48%, p-value < 0.001), and gonorrhea infection (15% vs. 4%, p-value=0.002). Leukorrhea was associated with a 4-fold increased risk of Trichomonas infection.Discussion:Leukorrhea on microscopy was associated with Trichomonas vaginitis. Patients with leukorrhea should be evaluated with more sensitive tests for T. vaginalis, preferably NAATs, if microscopy is negative.

Clients of female sex workers (FSWs) are an important bridging population for HIV and other sexually transmitted infections. However, the extent of risk to female noncommercial partners (NCPs) of clients has not been explored.Data originated from a cross-sectional behavioral and biological survey of FSW clients from 5 districts in Karnataka state, southern India. Clients were classified into 3 groups: married, single with at least 1 NCP, and single without an NCP. Bivariate and multivariable logistic regression models were constructed to examine the association between group membership and condom use patterns with FSWs and, where applicable, NCPs. HIV, herpes simplex virus type 2 (HSV-2), and other sexually transmitted infections were examined. Normalized weights were used to account for a complex sampling design.Most respondents in our sample (n = 2328) were married (61%). Compared with single respondents without an NCP, married clients were more likely to never use condoms with both occasional (adjusted odds ratio [AOR], 1.8; 95% confidence interval [CI], 1.3-2.5; P < 0.0001) and regular (AOR, 1.7; 95% CI, 1.1-2.6; P = 0.015) FSWs. Among clients with an NCP, married clients were at higher odds of never using a condom with their NCP (AOR, 5.5; 95% CI, 3.7-8.1; P < 0.0001). Overall prevalence for HIV, HSV-2, syphilis, and chlamydia or gonorrhea infection was 5.7%, 28.3%, 3.6%, and 2.1%, respectively. The prevalence of HSV-2 was 37%, 16%, and 19% among those who were married, those single without an NCP, and those single with an NCP, respectively.Married respondents were least likely to use condoms with both commercial and noncommercial sexual partners, while also having the highest prevalence of HSV-2. These results illustrate the risk posed to both commercial partners and NCPs of married clients.

The residential segregation of black populations, often in areas of high-economic disadvantage and low social status, may play a crucial role in the observed racial inequities in sexually transmitted disease rates.An ecological analysis of 2005 to 2009 average gonorrhea rates was performed across 277 US metropolitan statistical areas (MSAs). The black isolation index and Gini index of income inequality were used as proxy measures for racial and economic residential segregation respectively, derived from 2005 to 2009 US Census estimates. We used logistic regression modeling to produce estimates of odds ratios (ORs) and 95% confidence intervals (CIs) for the association between the segregation indices, both independently and in combination, on gonorrhea rates in MSAs. Effect measure modification was assessed by calculating the relative excess risk due to interaction between the 2 indices.Compared with MSAs with low levels of racial segregation, MSAs with high levels of racial segregation had increased odds of high gonorrhea rates (adjusted OR, 3.37; 95% CI, 1.23-9.21). Similarly, higher levels of income inequality predicted higher gonorrhea rates, although this association did not persist after adjustment for potential confounders (adjusted OR, 1.54; 95% CI, 0.74-3.24). In combined models, the influence of racial residential segregation on gonorrhea rates was stronger than that of income inequality-based segregation; there was no evidence of additivity or a multiplicative interaction.Residential segregation by race or income equality may be a key component in the perpetuation of high rates of gonorrhea and other sexually transmitted diseases among black populations in the United States.

Men who have sex with men (MSM) who report receptive anal intercourse (RAI) are currently recommended to undergo at least annual screening for rectal Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (GC) infection.Using standard culture methods, we assessed the prevalence of rectal GC/CT among MSM who reported RAI in the last year (n = 326) at an urban sexually transmitted disease (STD) clinic in a midwestern US city. A subset (n = 125) also underwent rectal GC/CT screening via nucleic acid amplification testing. We examined the associations between HIV status and prevalence of rectal GC and rectal CT using unadjusted and adjusted logistic regression models.The prevalence of rectal GC, rectal CT, and either rectal infection was 9%, 9%, and 15% by culture and 24%, 23%, and 38% by nucleic acid amplification testing, respectively. HIV was not associated with rectal GC prevalence in unadjusted or adjusted analyses. HIV-positive status was significantly associated with increased rectal CT prevalence in unadjusted models (odds ratio, 2.18; 95% confidence interval, 1.04-4.60); this association increased after multivariable adjustment (odds ratio, 3.14; 95% confidence interval, 1.37-7.19).Men who have sex with men reporting RAI had a high prevalence of rectal GC and rectal CT. HIV-positive status was significantly associated with prevalent rectal CT but not with prevalent rectal GC.