TRENDS IN REPORTED SEXUAL BEHAVIOR AND Y-CHROMOSOMAL DNA DETECTION AMONG FEMALE SEX WORKERS IN THE SENEGAL PrEP DEMONSTRATION PROJECT.

BACKGROUND: Pre-exposure prophylaxis (PrEP) can reduce HIV acquisition among female sex workers (FSW). However, changes in condomless sex frequency after PrEP initiation could reduce PrEP effectiveness when PrEP adherence is suboptimal as well as increase the risk of acquiring other sexually transmitted infections (STIs). Objective measures of condomless sex may be more accurate for determining changes in sexual behavior than self-reported measures. METHODS: We longitudinally measured self-reported condom use, number of clients, and presence of Y-chromosomal DNA (Yc-DNA) in vaginal swabs among 267 FSW accessing PrEP at four clinics in Senegal between 2015 and 2016. We assessed trends in sexual behavior over time since PrEP initiation using generalized estimating equations and evaluated predictors of Yc-DNA detection. RESULTS: We found no increase in self-reported condomless sex with clients (odds ratio (OR)=0.94; 95% CI: [0.89, 1.00]), main partners (OR=0.99; 95% CI: [0.96, 1.02]) or Yc-DNA detection (OR=0.99; 95% CI: [0.90, 1.08]) over time since initiation. Yc-DNA was detected in 34/154 (22%) of swabs tested and in 15/58 (26%) of swabs from FSW reporting consistent condom use among both clients and main partners. Self-reported condom use with clients or main partners did not predict Yc-DNA detection. CONCLUSIONS: In a FSW PrEP demonstration project in Senegal, we found no evidence of risk compensation among FSW on PrEP as measured by self-reported behavior or through Yc-DNA detection. Yc-DNA detection was frequently detected among FSW reporting consistent condom use, highlighting limitations of self-reported sexual behavioral measures.