Use of hair analysis for confirmation of self-reported cocaine use in users with negative urine tests

Introduction: Identification of cocaine use based on a urine test may miss many cases because of the short elimination half-life of the drug. Our obje ctive was to verify the sensitivity of the cocaine hair test in admitted us ers. Patients and Methods: Admitted cocaine users (38), that were 18-70 Yea rs of age and reported to have refrained from using cocaine in the few days to months prior to the test, it-ere compared to 10 controls who claimed ne ver to have used cocaine. All had negative urine tests for cocaine and benz oylecgonine by thin-layer chromatography. Cocaine and benzoylecgonine were extracted from unwashed hair and tested by established immunoassays. Result s: The hair test was positive in 37/38 cases (97%) and in none of the contr ols. There was significantly more cocaine in black hair than in brown or bl onde hair per mg of cocaine dose reported to have been consumed, highlighti ng a potential bias when interpreting test results in individuals with dark hair. There was a statistically significant correlation between reported d ose used and hair concentrations of cocaine. Discussion: The cocaine hair t est appears to be highly sensitive and specific in identifying past cocaine use in the setting of a negative urine test.