Biomarker validation of self-reported sex among middle-aged female sex workers in China

Purpose: The objective of this study was to examine information bias arising from self-reported sexual activity and its association with syphilitic infections among female sex workers (FSWs) aged 35 years and older in China. Methods: A questionnaire was administered to 1245 middle-aged FSWs. Respondents self -reported sexual intercourse in the past 48 hours. The prostate -specific antigen test was used to verify self reported sexual activity. FSWs were considered discordant if they indicated no sexual intercourse in the past 48 hours on the questionnaire and had a positive prostate -specific antigen test. Logistic regression was used to assess the associations between discordance and syphilis. Results: Three hundred twenty FSWs self-reported no engagement in sexual intercourse in the past 48 hours. One-fourth of respondents (25%) were discordant. Twenty-two percent and 35.8% of discordant FSWs tested positive for active and prevalent syphilis, respectively. After adjusting for confounders, discordant FSWs had 3.8 times the odds of active syphilis (95% confidence interval: 1.52-9.30) and 2.6 times the odds of prevalent syphilis (95% confidence interval: 1.37-5.02), compared with concordant FSWs. Conclusions: FSWs who had active or prevalent syphilis were more likely to be discordant. Data collected via self-reported questionnaire may not be a valid tool to assess sexual behavior. (C) 2017 Elsevier Inc. All rights reserved.