P18.05 Contribution of biomarkers to the validation of self-reported condom use in a treatment as prevention and a pre-exposure prophylaxis demonstration study among female sex workers

Abstract

Introduction The phenomenon of condom migration remains a major concern whenever a new HIV prevention approach is being considered to strengthen the existing preventive arsenal. We are currently measuring the baseline condom use at the recruitment visit of an on-going demonstration study on pre-exposure prophylaxis (PrEP) and treatment as prevention (TasP), involving female sex workers (FSWs) in Cotonou, Benin, West Africa. Methods During the recruitment visit, data on unprotected sex were collected through face-to-face interviews, from the first 112 FSWs with available biomarker results, recruited as of February 28, 2015. In addition, vaginal samples were tested for prostate-specific antigen (PSA) and Y chromosome DNA (Yc-DNA) PCR tests, to validate the self-reported unprotected sex. Additional biomarkers include gonorrhoea and chlamydia testing using nucleic-acid amplification tests and urine pregnancy tests. Performance parameters of the self-reported unprotected sex were calculated using combined results of all biomarkers as gold standard for recent semen exposure. Results The prevalence of recent self-reported unprotected sex with all types of sexual partners was 31.2% (35/112) vs. 51.8% (58/112) according to the combined biomarkers (p = 0.003, McNemar test). Using the combined biomarkers as gold standard, the sensitivity and specificity of self-reported unprotected sex were 34.5% and 72.2%, respectively. The prevalences of gonorrhoea and chlamydia at the recruitment visit were 8.0% (9/112) and 6.2% (7/112), respectively. Either infection was present in 16 participants (14.3%), out of whom 10 were positive for PSA or Yc-DNA PCR. The pregnancy test was positive for two participants of whom one was positive for both PSA and Yc-DNA PCR. Conclusion These results confirm the questionable validity of self-reported condom use among FSWs. They underscore the need of supplementing self-reported data by biomarkers to improve data reliability. These early results are part of the baseline data that will be subsequently used to look for condom migration. Disclosure of interest statement This study is funded by the Bill and Melinda Gates Foundation, and Truvada® for pre-exposure prophylaxis is provided free of charge by Gilead Sciences, Inc.