Testing for amphetamine-type stimulant (ATS) use to ascertain validity of self-reported ATS use among young female sex workers in Cambodia

Cross-sectional data from the Young Women's Health Study-2 (YWHS-2), a prospective study of HIV and STS use among young (15 to 29 years) FSW in Phnom Penh, Cambodia, was analyzed. The YWHS-2 assessed socio-demographic characteristics, HIV serology, HIV risk, and ATS use by self-report and urine toxicology testing at each quarterly visit; the 2nd of which provided data for this assessment. Outcomes include sensitivity, specificity, positive- and negative predictive values, overall and stratified by age, sex work setting and HIV status.Among 200 women, prevalence of positive toxicology screening for ATS use was 14% (95% CI: 9.2 - 18.9%) and concurrent prevalence of self-reported ATS was 15.5% (95% CI: 10.4- 20.6%). The sensitivity and specificity of self-report compared to toxicology test result was 89.3% (25/28), and 96.5% (166/172), respectively. The positive predictive value of self-report ATS use was 80.6% (25/31); the negative predictive value was 98.2% (166/169). Some differences in concordance between self-report and urine toxicology results were noted in analyses stratified by age group and type of sex-work setting, but not by HIV status.Results indicate a high prevalence of ATS use among high-risk young women in Phnom Penh, Cambodia and high concordance between self-reports and toxicology testing.