The validity of hair analysis for detecting cocaine and heroin use among addicts.

Radioimmunoassay of hair (RIAH) was compared with two criterion measures, confidential EMIT urinalysis and self-reporting of cocaine/heroin use, for a purposive sample of 134 persons in methadone treatment. Positive or negative RIAH was "confirmed" by urinalysis and/or self-report in 87 and 84% of the cases for cocaine and heroin (morphine), respectively. Corroborative evidence indicated that "excess" RIAH positives were attributable to the narrow window of detection for urinalysis (2 days), failure to admit drug use even to researchers, and/or inadvertent ingestion of small amounts of drug. A global self-report of cocaine use intensity was related to amount in the hair.