Use of hair testing Use of hair as a test medium avoids the limitations of infrequent urine testing. Hair testing is relatively well established and uses a number of the same technologies as urine-based tests, including enzyme, radioisotope, and fluorescent immunoassays. Urinalysis of a single specimen generally can detect the presence of drugs for a period of several days to a week or two, depending on the drug. Compared with urine samples, it presents fewer risks of disease transmission. Preliminary research shows that even treating hair with a variety of strong compounds will not completely eliminate traces of illicit drugs.
Metabolites are the biochemical products of the breakdown of drugs within the body.
Once a drug metabolite is embedded in the hair sheath, a process which appears to occur while the hair is being formed in its follicle, the metabolite is very nearly permanent. As the hair shaft grows, it forms a longitudinal record of the compounds it has absorbed, including drugs of abuse. Additional research is needed to better understand such issues as the biochemical processes of the absorption of drugs and their metabolites into hair, dose-related cutoff levels, and the influence of external contamination. NIJ is currently conducting studies on these issues. Funded by NIJ and the Pinellas County Sherrif's Department, the project was similar to NIJ's DUF program.