Scientific issues in drug testing. Council on Scientific Affairs.

Testing for drugs in biologic fluids, especially urine, is a practice that has become widespread. The technology of testing for drugs in urine has greatly improved in recent years. Inexpensive screening techniques are not sufficiently accurate for forensic testing standards, which must be met when a person's employment or reputation may be affected by results. This is particularly a concern during screening of a population in which the prevalence of drug use is very low, in which the predictive value of a positive result would be quite low. Physicians should be aware that results from drug testing can yield accurate evidence of prior exposure to drugs, but they do not provide information about patterns of drug use, about abuse of or dependence on drugs, or about mental or physical impairments that may result from drug use.