Recent Biomarker-Confirmed Unprotected Vaginal Sex, But Not Self-reported Unprotected Sex, Is Associated With...

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.

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.

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).

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.