Comparison of Chlamydia trachomatis Seroprevalence and Risk Factors for Infection Among Women who have Sex with Women and Women who have Sex with Men in the 2013-2016 cycles of the National Health and Nutrition Examination Survey, United States

Little is known about the lifetime prevalence and risk factors for sexually transmitted infections (STIs) among cisgender women who have sex with women (WSW), despite this subpopulation being at risk for STIs. Using data from a large, nationally-representative survey, we estimated the seroprevalence of Chlamydia trachomatis (CT) among WSW and compared it to seroprevalence in women who have sex with men (WSM). We also identified factors that may be associated with an increased or decreased risk of ever having had CT infection. Methods: Publicly available CT serological data from sexually experienced women aged 18-39 participating in the 2013-2014 and 2015-2016 cycles of the National Health and Nutrition Examination Survey (NHANES) were used to estimate weighted seroprevalence in WSW and WSM. WSW were defined as women who reported ever having had sex with a woman in their lifetime, while WSM reported having had sex with a man but never having had sex with a woman in their lifetime. Seropositivity was determined by the detection of Pgp3 antibodies to CT using an ELISA assay. We used Poisson regression with robust standard errors to identify factors associated with CT seropositivity in each group, and to estimate the association between WSW and CT seroprevalence, adjusted for factors associated with CT seropositivity in both groups. Results: WSW were younger, had a younger age at sexual debut, and more lifetime male sex partners than WSM. The weighted CT seroprevalence in WSM (n=1207) was 28.6% (95% CI: 24.4, 32.9) and 38.4% (95% CI: 30.0, 46.9) in WSW (n=218). After adjusting for age, race/ethnicity, income-poverty ratio, age at sexual debut, number of lifetime male sex partners, having chlamydia in the past year, and sexual identity, there was no significant difference in CT seroprevalence between WSM and WSW (aPR=1.22 [95% CI: 0.98, 1.53], p=0.07). A non-Hispanic Black or an “other” race/ethnicity, a higher lifetime number of male sex partners, and a history of CT in the last year was associated with higher CT seroprevalence in both WSW and WSM. Among WSM, individuals reporting a Hispanic race/ethnicity, an income below the income/poverty ratio, and a younger age at sexual debut also had higher CT seroprevalence. Sexual identity was not associated with seroprevalence in WSM, but among WSW, individuals who identified as bisexual had lower CT seroprevalence than WSW who identified as straight. Conclusion: WSW had comparable CT seroprevalence with WSM after adjusting for sociodemographic characteristics, sexual behavior characteristics, and recent CT infection, indicating that the risk for CT infection may be comparable in these two groups. Given their younger age at sexual debut and likelihood of having male as well as female partners, providers should follow the same CT screening guidelines for WSW as they do for WSM.