title: Biomarker validation of recent unprotected sexual intercourse in a prospective study of young women engaged in sex work in Phnom Penh, Cambodia.
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.
authors.affiliation: Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, CA 94105, USA. jevans@epi.ucsf.edu
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Evans
authors.forename: Marie-Claude
authors.initials: MC
authors.lastname: Couture
authors.forename: Ellen S
authors.initials: ES
authors.lastname: Stein
authors.forename: Neth
authors.initials: N
authors.lastname: Sansothy
authors.forename: Lisa
authors.initials: L
authors.lastname: Maher
authors.forename: Kimberly
authors.initials: K
authors.lastname: Page
mesh_terms: D000293:Adolescent; D000328:Adult; D019969:Amphetamine-Related Disorders / Q000150:complications; D015415:Biomarkers / Q000032:analysis*; D002160:Cambodia; D017280:Condoms / Q000706:statistics & numerical data*; D005260:Female; D015658:HIV Infections / Q000517:prevention & control; D006801:Humans; D008297:Male; D011446:Prospective Studies; D017430:Prostate-Specific Antigen / Q000032:analysis*; D057566:Self Report; D012661:Semen / Q000737:chemistry / Q000378:metabolism; D011477:Sex Work / Q000706:statistics & numerical data*; D060386:Sex Workers / Q000706:statistics & numerical data*; D012747:Sexual Partners; D047568:Unsafe Sex / Q000706:statistics & numerical data*; D055815:Young Adult
chemical_list: D015415:Biomarkers; D017430:Prostate-Specific Antigen