Results of a baseline urine test predict levels of cocaine use during treatment.

Sixty-one cocaine dependent outpatients submitted a single urine sample at least 1 week prior to entry into a 4-week treatment study. Participants were then expected to provide three urine samples per week during the month of treatment. The 61 patients studied here all completed treatment and provided an average of more than 11 of 12 scheduled urine samples. Participants who submitted a cocaine-positive sample prior to treatment provided more positive urine samples during the 4-week trial, were less likely to be completely abstinent during the month, and took longer to reach an initial abstinence criterion of three consecutive cocaine-free urines. Thus, a single pretreatment urine test represents a powerful predictor of subsequent cocaine use. The results suggest that future randomized trials stratify group assignment based on the results of a baseline urine test.