Urinalysis Testing for Cocaine
Urine samples were collected under same-sex staff observation and tested immediately onsite for the cocaine metabolite benzoylecgonine (150 ng/mL) using qualitative dipsticks. Urinalysis outcomes were the percentage of scheduled samples testing negative for cocaine, total number of negative samples, longest duration of continuous abstinence, and percentage of participants providing 3 negative samples during week 26 (ie, the end of intervention) and week 30 (ie, the end of study). Data were analyzed separately during weeks 7 to 26 (active incentives), 27 to 30 (after incentives), and week 30 (final evaluative period).