Hair Analysis in Drugs-of-Abuse Testing

Compounds trapped in hair during growth collect and remain in the mature hair strand. Defined lengths of the hair strand can be analyzed to provide information on ingestion of a substance during the window of time corresponding to the growth period of the segment of hair analyzed. Both screening (immunoassay) and confirmation (liquid chromatography-tandem mass spectrometry, gas chromatography-mass spectrometry, gass chromatography-tandem mass spectrometry) methods for drugs in hair require methods of liquefaction and/or extraction of the solid hair fiber. Extensive washing of hair samples to remove external contamination and/or drugs from sweat prior to analysis is integral to a meaningful hair result, particularly to distinguish use from contamination and to utilize the hair’s ability to reflect dose. Some results of drugs-of-abuse analysis in washed hair of proven drug users ranged (in ng/10 mg hair) from the cut-offs to 2270 (cocaine), 559 (morphine), 79 (methamphetamine), and 150 (phencyclidine). The metabolite of cannabis use, carboxy-tetrahydrocannabinol, was present in users’ hair samples in amounts up to 76 pg/10 mg hair. Hair analysis for drugs of abuse is most widely used for pre-employment and workplace testing, but has also shown utility in criminal justice settings, for diagnostic and monitoring purposes in rehabilitation programs, in determining prenatal drug exposure, and other arenas.