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A Comparison of Two Mathematical Modeling Frameworks for Evaluating Sexually Transmitted Infection Epidemiology

imageBackground: Different models of sexually transmitted infections (STIs) can yield substantially different conclusions about STI epidemiology, and it is important to understand how and why models differ. Frequency-dependent models make the simplifying assumption that STI incidence is proportional to STI prevalence in the population, whereas network models calculate STI incidence more realistically by classifying individuals according to their partners' STI status. Methods: We assessed a deterministic frequency-dependent model approximation to a microsimulation network model of STIs in South Africa. Sexual behavior and demographic parameters were identical in the 2 models. Six STIs were simulated using each model: HIV, herpes, syphilis, gonorrhea, chlamydia, and trichomoniasis. Results: For all 6 STIs, the frequency-dependent model estimated a higher STI prevalence than the network model, with the difference between the 2 models being relatively large for the curable STIs. When the 2 models were fitted to the same STI prevalence data, the best-fitting parameters differed substantially between models, with the frequency-dependent model suggesting more immunity and lower transmission probabilities. The fitted frequency-dependent model estimated that the effects of a hypothetical elimination of concurrent partnerships and a reduction in commercial sex were both smaller than estimated by the fitted network model, whereas the latter model estimated a smaller impact of a reduction in unprotected sex in spousal relationships. Conclusions: The frequency-dependent assumption is problematic when modeling short-term STIs. Frequency-dependent models tend to underestimate the importance of high-risk groups in sustaining STI epidemics, while overestimating the importance of long-term partnerships and low-risk groups. 03/01/2016 01:00 AM
 

Racial Differences in Receipt of Chlamydia Testing Among Medicaid-Insured Women in 2013

imageObjective: To estimate the percentage of young, sexually active Medicaid-insured women who were tested for chlamydia by age, race/ethnicity, and history of sexually transmitted disease (STD) diagnosis. Methods: We used the medical diagnostic and procedural codes from Truven Health MarketScan Medicaid claims data from 10 states in 2012 and 2013 to estimate the rates of chlamydia testing in 2013 and previous STD diagnosis (diagnosed in 2012) among Medicaid-insured women aged 15–25 years who were sexually active in 2013. We also used a logit model to assess the association between chlamydia testing and women's age, race/ethnicity, and previous STD diagnosis. Results: Overall, among approximately 261,000 Medicaid-insured women aged 15–25 years in 2013 who were classified as sexually active, 50.2% were tested for chlamydia in 2013. The chlamydia testing rate was 45.6% for white women and 57.5% for black women. The chlamydia testing rate was 63.5% for women diagnosed as having an STD in 2012 and 46.8% for women not diagnosed as having an STD in 2012. The chlamydia testing rate was significantly (P < 0.05) associated with previous STD diagnosis, age, and race/ethnicity in our logit model. Conclusions: Higher chlamydia testing rates among black women can be explained in part by higher rates of previous STD diagnoses. Our finding that black women have the highest chlamydia testing rates is encouraging, as improved access to STD prevention services among racial/ethnic minorities can help to reduce racial/ethnic disparities in STDs. However, chlamydia screening remains an underused preventive health service for young women of all racial and ethnic groups. 03/01/2016 01:00 AM
 

Measuring Health and Quality of Life for Women Undergoing Testing and Screening for Chlamydia: A Systematic Review

imageBackground: Most economic evaluations of interventions to prevent or control curable sexually transmitted infections (STIs), such as chlamydia, have focused on the longer-term health impacts avoided. However, there is a range of qualitative evidence suggesting that those who think that they might have an STI and/or undergo testing can experience impacts on their quality of life (QoL) at the testing and diagnosis stage. A systematic review was undertaken to identify and evaluate studies that have measured QoL and sexual health for women undergoing testing and screening for chlamydia. Methods: A systematic review was conducted, with searches of 5 electronic databases up to the end of August 2013. Data on study characteristics, methods, and results were extracted using a standard template, and a narrative synthesis was undertaken. Results: Eight studies measuring QoL and sexual health were included. The included studies measured a variety of aspects of QoL and sexual health, with a focus on psychosocial well-being. A range of validated tools were used to measure health and QoL, and “bespoke” questions were also developed. Few significant differences were found with comparator groups using generic instruments, but some impacts were found using bespoke questions. Conclusions: Although researchers have begun to examine the relationships between QoL and sexual health, there are limitations associated with the evidence available. There is, thus, a need for further research exploring sexual health and QoL for patients undergoing testing and screening for curable STIs, with a focus on analyzing the most appropriate methodological approaches in this context. 03/01/2016 01:00 AM
 

Characteristics Associated With Urethral and Rectal Gonorrhea and Chlamydia Diagnoses in a US National Sample of Gay and Bisexual Men: Results From the One Thousand Strong Panel

imageBackground: Gay and bisexual men are at elevated risk for Neisseria gonorrhoeae and Chlamydia trachomatis (GC/CT). Rectal GC/CT symptoms may be less obvious than urethral, increasing opportunities for undiagnosed rectal GC/CT. Methods: A US national sample of 1071 gay and bisexual men completed urethral and rectal GC/CT testing and an online survey. Results: In total, 6.2% were GC/CT positive (5.3% rectal, 1.7% urethral). We calculated adjusted (for education, race, age, relationship status, having health insurance, and income) odds ratios for factors associated with rectal and urethral GC/CT diagnoses. Age was inversely associated with urethral and rectal GC/CT. Compared with white men, Latinos had significantly greater odds of rectal GC/CT. Among men who reported anal sex, those reporting only insertive sex had lower odds of rectal GC/CT than did men who reported both insertive and receptive. There was a positive association between rectal GC/CT and number of male partners (<12 months), the number of anal receptive acts, receptive condomless anal sex (CAS) acts, and insertive CAS acts. Compared with those who had engaged in both insertive and receptive anal sex, those who engaged in only receptive anal sex had lower odds of urethral GC/CT. The number of male partners (<12 months) was associated with increased odds of urethral GC/CT. Conclusions: Rectal GC/CT was more common than urethral and associated with some demographic and behavioral characteristics. Our finding that insertive CAS acts was associated with rectal GC/CT highlights that providers should screen patients for GC/CT via a full range of transmission routes, lest GC/CT go undiagnosed. 03/01/2016 01:00 AM
 

Recent Biomarker-Confirmed Unprotected Vaginal Sex, But Not Self-reported Unprotected Sex, Is Associated With Recurrent Bacterial Vaginosis

imageBackground: Self-reported unprotected vaginal sex seems to increase risk of bacterial vaginosis (BV). However, the validity of self-reports is questionable, given their inconsistency with more objective measures of recent semen exposure such as detection of prostate-specific antigen (PSA). We examined whether recent unprotected sex, as measured both by PSA detection on vaginal swabs and by self-report, was associated with increased BV recurrence. Methods: We analyzed randomized trial data from nonpregnant, BV-positive adult women recruited from a sexually transmitted disease clinic. Participants received BV therapy at enrollment and were scheduled to return after 4, 12, and 24 weeks. Bacterial vaginosis (by Nugent score) and PSA were measured at each visit. We used Cox proportional hazards models to examine the association between PSA positivity and recurrent BV. We also evaluated associations between self-reported unprotected sex (ever/never since the last visit and in the last 48 hours, analyzed separately) and recurrent BV. Results: Prostate-specific antigen and BV results were available for 96 women who contributed 226 follow-up visits. Prostate-specific antigen positivity was associated with increased BV recurrence (adjusted hazard ratio [aHR], 2.32; 95% confidence interval [CI], 1.28–4.21). In contrast, we observed no significant increase in BV recurrence among women self-reporting unprotected sex since the last visit (aHR, 1.63; 95% CI, 0.77–3.43) or in the last 48 hours (aHR, 1.28; 95% CI, 0.70–2.36). Conclusions: Estimates from earlier studies linking self-reported unprotected sex and BV may be biased by misclassification. Biomarkers can improve measurement of unprotected sex, a critical exposure variable in sexual health research. 03/01/2016 01:00 AM
 

Prevalence and Correlates of a Diagnosis of Sexually Transmitted Infection Among Young Aboriginal and Torres Strait Islander People: A National Survey

imageBackground: Young Aboriginal and Torres Strait Islander (Aboriginal) people are recognized as a priority population for the control of sexually transmissible infections (STIs) in Australia. This article reports the prevalence of self-reported STI diagnoses and their correlates among Aboriginal people aged 16 to 29 years. Methods: Results were analyzed from a survey conducted between 2011 and 2013 at regular community events. Univariate and multivariate logistic regression models were used to identify the correlates of a history of STI diagnosis among participants who reported being sexually active and ever having been tested for STIs. All analyses were stratified by sex. Results: Of the 2877 participants in this study, 2320, comprising 60% females, self-reported ever having had vaginal or anal sex, and a further subset of 1589 (68%) reported ever being tested for any of the following STIs: chlamydia, gonorrhea, syphilis, or trichomonas. Within this latter group, the proportion who reported that they had had a positive STI diagnosis was 25%. In multivariate analysis, women who reported sexual debut before the age of 16 years (prevalence ratio [PR], 1.53; 95% confidence interval, 1.16–2.81; P < 0.05), ever having had oral sex (PR, 2.66; 1.47–4.82; P < 0.001), inconsistent condom use in the past 12 months (PR, 1.71; 1.13–2.58; P < 0.012), having had sex with someone they had just met (adjusted odds ratio, 1.74; 1.21–2.50; P < 0.003), and using ecstasy (PR, 1.81; 1.16–2.81; P < 0.009) were significantly associated with a self-reported history of an STI diagnosis. For men, being older (25–29 years; PR, 2.10; 1.10–3.96; P < 0.023), being gay or bisexual (PR, 2.22; 1.16–4.27; P < 0.016), not using a condom during last sex, (PR, 1.74; 1.10–2.76; P < 0.019), past ecstasy use (PR, 1.88; 1.11–3.20; P < 0.019), and injecting drug use (PR, 2.81; 1.35–5.88); P < 0.006) were independent predictors of ever reporting being diagnosed as having an STI. Discussion: In the first community-based survey of this population, a self-reported history of ever being diagnosed as having prevalent STIs was common in sexually active young Aboriginal people who reported STI testing in the past. This population requires targeted education and health service interventions to address the high burden of STIs. 03/01/2016 01:00 AM
 

Predictors of Human Papillomavirus Vaccination Among Young Men Who Have Sex With Men

imageBackground: Human papillomavirus (HPV) is a common sexually transmitted infection that causes anal, penile, and oropharyngeal cancers in men. Men who have sex with men (MSM) are at particularly high risk for HPV infection and HPV-related disease. Human papillomavirus vaccination is currently recommended for all MSM in the United States through age 26 years, yet little is known about HPV vaccine uptake in this population. The purpose of this study was to identify predictors of HPV vaccine uptake and barriers and facilitators to HPV vaccination that may be unique to young MSM. Methods: Men aged 18 to 26 years (n = 336) were recruited via advertisements placed on a geospatial smartphone dating application designed for MSM. Participants completed an online survey. Correlates of vaccine uptake and provider recommendation for HPV vaccine were identified using logistic regression. Results: In total, 21% of participants had received at least 1 dose of HPV vaccine. Provider recommendation was the strongest predictor of uptake such that MSM with a recommendation were more than 40 times more likely to have been vaccinated. Additional predictors of uptake included age and HPV vaccine attitudes. Predictors of provider recommendation included sexual identity, race/ethnicity, condomless anal sex, and HIV status. Psychosocial correlates and barriers and facilitators to HPV vaccination among unvaccinated men were also identified. Conclusions: Findings highlight potential disparities in HPV vaccine uptake, as well as disparities in provider recommendation practices for HPV vaccination. Future interventions should aim to clarify misconceptions, modify psychosocial beliefs, and address barriers and facilitators to HPV vaccine uptake specific to young MSM. 03/01/2016 01:00 AM
 

Determinants of High-Risk Human Papillomavirus Seroprevalence and DNA Prevalence in Mid-Adult Women

imageBackground: The epidemiology of high-risk human papillomavirus (hrHPV) infections in mid-adult women is not well understood. Methods: We conducted a cross-sectional analysis of 379 women 30 to 50 years of age. Vaginal samples were tested for type-specific HPV DNA by polymerase chain reaction. Sera were tested for type-specific HPV antibodies by Luminex-based assay. Assays included 13 hrHPV types (16/18/31/33/35/39/45/51/52/56/58/59/68). Self-reported health and sexual history were ascertained. Risk factors for seropositivity and DNA positivity to hrHPV were assessed in separate Poisson regression models. Results: The mean (SD) age of participants was 38.7 (6.1) years, and the median lifetime number of male sex partners was 7. Approximately two-thirds (68.1%) were seropositive for any hrHPV, 15.0% were DNA positive, and 70.7% were seropositive or DNA positive. In multivariate analyses, women who were married/living with a partner were less likely to be seropositive than single/separated women (adjusted prevalence ratio [aPR], 0.86; 95% confidence interval [CI], 0.75–0.98). Compared with never hormonal contraceptive users, current (aPR, 1.53; 95% CI, 1.01–2.29) or former (aPR, 1.64; 95% CI, 1.10–2.45) users were more likely to be seropositive. Women with a lifetime number of sex partners of 12 or more were more likely to be seropositive compared with those with 0 to 4 partners (aPR, 1.29; 95% CI, 1.06–1.56). Similar associations were seen with DNA positivity. In addition, there was a positive association between current smoking and hrHPV DNA (aPR vs. never smokers, 2.51; 95% CI, 1.40–4.49). Conclusions: Seventy-one percent of mid-adult women had evidence of current or prior hrHPV infection. Measures of probable increased exposure to HPV infection were associated with both seropositivity and DNA positivity to hrHPV, whereas current smoking was positively associated with hrHPV DNA only. 03/01/2016 01:00 AM