An estimated 3.7 million people in the United States are currently infected with Trichomonas vaginalis, a sexually transmitted infection (STI) caused by the protozoan T. vaginalis.1 The prevalence of T. vaginalis infections among sexually active women varies widely, with estimates of 5% among women in family planning clinics, 10% among women using an Internet-based screening program, and as high as 37% among incarcerated women.2–5 Clinical signs and symptoms include vaginitis and vaginal discharge; however, it is estimated that most men and approximately half of women are asymptomatic.6–8 This is especially problematic given that untreated T. vaginalis is associated with serious health consequences including preterm birth, low birth weight, infertility, pelvic inflammatory disease, and increased risk of HIV.9–13
Although T. vaginalis is the most common curable STI in the United States, it continues to be overlooked and underdiagnosed.14 Identifying factors associated with T. vaginalis will serve as key evidence needed for targeted screening recommendations. The objective of this study was to determine the prevalence and correlates of T. vaginalis using newly available and highly sensitive nucleic acid amplification tests (NAATs) in multiple populations of high-risk women. We used remnant specimen collected from September to December 2010 from women being screened for chlamydia/gonorrhea at four different venue types in Los Angeles County, California, including the following: (1) public sexually transmitted disease (STD) clinics (n = 12), (2) an Internet-based home-testing program (www.dontthinkknow.org), (3) an adult correctional facility, and (4) a juvenile detention facility. The study population varied at each venue type such that chlamydia/gonorrhea testing was conducted in girls entering juvenile hall (ages 11–18 years), females seen at the STD clinics (12 years and older), and females using the home test kit (ages 12–25 years). In the jail setting, however, women aged 18 to 30 years were routinely screened for chlamydia/gonorrhea, whereas women older than 30 years were only screened if they were possibly pregnant or incarcerated on a sex-related charge. The remnant specimens used for routine chlamydia/gonorrhea NAATs were tested using the APTIMA T. vaginalis assay (Hologic/Gen-Probe, San Diego, CA).
Some of the data for this project were collected as part of a larger study, and details have been previously described.4 Our study includes additional data including data from girls younger than 18 years and additional behavioral information from women tested in STD clinics. Differences between groups were evaluated using t tests and χ 2 methods, and associations between T. vaginalis and other factors were evaluated using logistic regression analysis. All analyses were conducted using SAS version 9.2 (SAS Institute Inc, Cary, NC). This study was approved by the human subjects committee at the Los Angeles County Department of Public Health and the University of California Los Angeles.
A total of 1215 remnant specimens from women undergoing routine chlamydia/gonorrhea screening were tested for T. vaginalis. The prevalence of T. vaginalis varied by venue type, with the highest prevalence noted among women testing through jail (22%), followed by the STD clinics (17%), and the lowest among women using home-test kits (7%; Table 1). Regardless of venue, the prevalence was higher among women with a concurrent chlamydia or gonorrhea infection, although the pattern varied by venue. For instance, among women in STD clinics, the prevalence of T. vaginalis was 80% among those coinfected with gonorrhea as compared with 16% among those without gonorrhea (P < 0.01). Even after adjusting for age and race/ethnicity, women at the STD clinics with a concurrent gonorrhea infection were more than 14 times as likely to have T. vaginalis when compared with those without gonorrhea (adjusted odds ratio [AOR]= 14.28; 95% confidence interval [CI], 2.23–91.71). Chlamydia coinfections were independently associated with T. vaginalis among girls in juvenile detention (AOR= 5.60; 95% CI. 2.40–13.07; Table 1).
Based on behavioral information available for women testing at STD clinics, we found that the prevalence of T. vaginalis varied by risk behaviors, with a lower prevalence among women with a new sex partner (10% vs. 20% in women with no new sex partner; P = 0.04) and a higher prevalence among women reporting substance use (31% vs. 12% in nonusers; P < 0.01; Table 2). Based on multivariable analysis, these factors were independently associated with T. vaginalis infection, with women with a new sex partner less likely to test positive for T. vaginalis (AOR, 0.35; 95% CI. 0.15–0.84) and those with substance use more likely to test positive for T. vaginalis (AOR, 3.14; 95% CI. 1.57–6.30; Table 1).
The use of highly sensitive testing technology (NAATs) allowed us to improve our understanding of the epidemiology of T. vaginalis across the different at-risk groups of women, including girls testing through a juvenile detention facility, a unique population not described before. We found that the prevalence of T. vaginalis was relatively high across all chlamydia/gonorrhea screening populations and certainly higher than the prevalence estimates of 3.2% among women in the United States.1 We also found substantial coinfections with chlamydia or gonorrhea and T. vaginalis across the different study populations. Findings in the literature on concurrent chlamydia/gonorrhea infections are mixed; however, two studies conducted in a clinical setting concur with our findings.2,15–17 This implies that there may be intersecting sexual networks, with high transmission probabilities for T. vaginalis among certain populations of women with gonorrhea or chlamydia. Moreover, these data suggest that testing and/or presumptive treatment of T. vaginalis may be indicated in women treated for gonorrhea in STD clinics or jails as well as girls treated for chlamydia in a juvenile detention. This study also adds to the evidence of others showing an association between T. vaginalis infections and incarceration among women.18–20 Because incarcerated women often have higher-risk sexual networks and are at increased risk for HIV infection, the diagnosis and treatment of T. vaginalis infections in this setting should be a high priority.
Interestingly, our results showed that women who reported a new sex partner were less likely to test positive for T. vaginalis. In trying to understand this association, we explored differences between those who reported a new sex partner and those who did not and found that women who had no new sex partners were older and more likely to report unprotected sex (48% never using condoms vs. 24%). Condom use was not consistently assessed (>30% missing), and therefore, this limits our interpretations. However, these findings may support other data that suggest that the risk of STI transmission may be increased in the context of regular partnerships, given that condom use in this context is usually lower.21
Several study limitations should be mentioned. T. vaginalis tests were performed on specimen collected as part of routine chlamydia/gonorrhea screening. Women in the older age groups (>26 years in STD clinics and >30 years in jail) were likely tested because of symptoms, contact with a positive partner, and so on, and potentially at higher risk. This could result in an overestimation of the true prevalence of T. vaginalis in this group and may bias the association between T. vaginalis and gonorrhea coinfections. However, in limiting our analysis to younger women in jail and the STD clinics, we found that the prevalence of T. vaginalis still remained significantly higher among younger women coinfected with gonorrhea (data not shown). Nevertheless, this study demonstrates that T. vaginalis is a common infection across varied populations of women. These findings highlight the need for targeted T. vaginalis screening recommendations and suggest that testing and/or presumptive T. vaginalis treatment should be considered in a subset of women, particularly in women treated for gonorrhea in jail or STD clinic settings and chlamydia in juvenile detention settings.
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