Improving second-generation surveillance: the biological measure of unprotected intercourse using prostate-specific antigen in vaginal secretions of West African women.

Second-generation surveillance for HIV includes measures of high-risk behaviors among the general adult population and sex workers (SW). Questionnaires are prone to social desirability biases because individuals minimize the frequency of behaviors not expected from them. The objective was to determine whether the prostate-specific antigen (PSA) could be used as a biological marker of unprotected intercourse. We measured the presence of PSA in vaginal secretions of women who were (n = 508) or were not (n = 658) SW presenting with vaginal discharge in health facilities of Ghana Togo Guinea and Mali. The cutoff for a positive assay was determined as = 0.4 µg/L based on a subsample of 95 non-SW claiming abstinence for 3 months. A positive PSA assay was correlated with infections with Neisseria gonorrhoeae Chlamydia trachomatis and Mycoplasma genitalium. Among non-SW a positive PSA was more common among those with HIV but less frequent in those better educated. Among SW and non-SW women from Ghana were less likely to have a positive PSA and had a lower prevalence of sexually transmitted infections than those from elsewhere. PSA can be used as a biological marker of unprotected intercourse allowing interventions to target efforts on those at highest risk. (authors)