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Sexually Transmitted Diseases:
doi: 10.1097/OLQ.0b013e318286db8a
Original Study

Biomarker Validation of Recent Unprotected Sexual Intercourse in a Prospective Study of Young Women Engaged in Sex Work in Phnom Penh, Cambodia

Evans, Jennifer L. MS*; Couture, Marie-Claude PhD*; Stein, Ellen S. MPH*; Sansothy, Neth MD; Maher, Lisa PhD; Page, Kimberly PhD, MPH* ; Young Women’s Health Study Collaborative

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Abstract

Background

Accurate measurement of unprotected sex is essential in HIV prevention research. Since 2001, the 100% Condom Use Program targeting female sex workers (FSWs) has been a central element of the Cambodian National HIV/AIDS Strategy. We sought to assess the validity of self-reported condom use using the rapid prostate-specific antigen (PSA) test among Cambodian FSWs.

Methods

From 2009 to 2010, we enrolled 183 FSWs in Phnom Penh in a prospective study of HIV risk behavior. Prostate-specific antigen test results from the OneStep ABAcard were compared with self-reported condom use in the past 48 hours at quarterly follow-up visits.

Results

Among women positive for seminal fluid at the first follow-up visit, 42% reported only protected sex or no sex in the detection period. Discordant results were more likely among brothel and street-based FSW versus entertainment (56% vs. 17%), recent (last 3 months) amphetamine-type stimulant (ATS) users (53% vs. 20%), and those with 5 or more partners in the past month (58% vs. 13%). In multivariable regression models, positive PSA results were associated with recent ATS use (adjusted risk ratio [ARR], 1.5; 95% confidence interval [CI], 1.1–2.2), having a nonpaying last sex partner (ARR, 1.7; CI, 1.2–2.5), and sex work venue (ARR, 3.0; CI, 1.4–6.5). Correspondingly, women with a nonpaying last sex partner were more likely to report unprotected sex (ARR, 1.5; CI, 1.1–2.2), but no associations were found with sex work venue or ATS use.

Conclusions

Results confirm the questionable validity of self-reported condom use among FSW. The PSA biomarker assay is an important monitoring tool in HIV/sexually transmitted infection research including prevention trials.

Copyright © 2013 American Sexually Transmitted Diseases Association All rights reserved.

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