Radioimmunoassay of hair for determination of cocaine, heroin, and marijuana exposure: comparison with self-report.

Radioimmunoassay of hair (RIAH) was compared with self-report for cocaine, heroin, and marijuana in two populations: 109 persons entering residential drug user treatment and 86 at follow-up posttreatment. Among treatment entrants, 89% of 87 RIAH cocaine-positives and 96% of 45 RIAH heroin-positives were confirmed by self-report. However, among those followed-up posttreatment, only 51% of 43 RIAH cocaine-positives and 67% of 18 RIAH heroin-positives were so confirmed. Whereas 95% of 104 self-reports of cocaine use in the combined population were confirmed by RIAH, only 69% of 80 self-reports of heroin use were. Self-report and RIAH for marijuana were weakly associated.