Condom Use and Vaginal Y-Chromosome Detection: The Specificity of a Potential Biomarker

Objective: Detection of vaginal Y-chromosome sequences (YCS) may be a useful biomarker to validate sexual behavior reporting in women. We describe the effects of condom use on the detection of vaginal YCS. Methods: Fifty-six women were asked to abstain from sexual inter course for 14 days. On day 15, participants were asked to engage in sexual intercourse with their male partners using condoms. Self-collected vaginal swabs were obtained on days 14,16, and 17. YCS were detected using the Roche LightCycler with the use of positive controls. Results: Fourty-four of 56 women completed the study. Five women (11.4%) had detectable YCS. The overall specificity of the YCS assay with condom use was 92% (95% Cl: 80%-98%). Although women who reported receptive oral sex and digital penetration within 48 hours of swab collection had a higher detection rate of YCS [RR 2.3 (95% Cl: 1.1-4.6) and 3.6 (95%CI: 1.6-8.5), respectively], the mean concentration of YCS was much less than that associated with unpro tected vaginal intercourse (P