Bias in Self-Reported Condom Use: Association Between Over-Reported Condom Use and Syphilis in a Three-Site Study in China

This study examined over-reporting bias in self-reported condom use and assessed its association with syphilis. A survey was conducted among 1245 female sex workers (FSWs) in three cities in China. Respondent’s over-reported condom use was defined as reporting no unprotected sex for the past 24 h but testing positive for prostate specific antigen. The proportion of prevalent syphilis and active syphilis was 23 and 10 % respectively among FSWs. The proportion of over-reported condom use with sex clients only was 27–45 % among the three study sites. The proportion of over-reported condom use with all sex partners (clients, husbands, or boyfriends) was 26–46 %. FSWs who had active or prevalent syphilis were more likely to over report condom use. Self-reported condom use may not be a valid tool to measure the efficacy of HIV/STI intervention because the bias is associated with the outcome measure, i.e., syphilis.