Objective: The objective of this study was to assess the validity of women's reports of recent unprotected sex by testing for prostate-specific antigen (PSA) in vaginal samples.
Study design: The authors conducted prospective research with 332 female sex workers attending 2 public dispensaries in Madagascar.
Results: Among women who reported no sex or protected sex only within the past 48 hours, 21% and 39%, respectively, tested positive for PSA. Among those testing positive for PSA, no differences in PSA concentrations were found among those reporting no sex, protected sex only, or at least one unprotected act.
Conclusions: The substantial disagreement between self-reports and measurement of a biologic marker of semen exposure in vaginal specimens substantiates that self-reports of sexual behavior cannot be assumed to be valid measures. Future sexually transmitted infection/HIV and pregnancy prevention studies should confirm the validity of self-reports or use end points that do not rely on self-reported data.