"Disadvantages for testing for drugs in hair are the high costs and the longer time needed to obtain results, compared with the time required by other matrices. Analysis of the hair specimen is a complex process that involves breaking down the hair to free the drugs trapped in it. This chemical process requires a longer time of analyses than other matrixes. It can be done only in a laboratory; no POCTs [Point Of Care Tests] are available for testing hair samples."


"Clinical Drug Testing in Primary Care," Technical Assistance Publication (TAP) 32, Substance Abuse and Mental Health Services Administration, Clinical Drug Testing in Primary Care (Rockville, MD: U.S. Departent of Health and Human Services, 2012), p. 22.