Focus on alcohol & drug abuse: ensuring validity in urine drug testing.

Methods for urine drug testing have been available for several decades. These procedures are useful in assessing and identifying substance use in treatment programs, research programs, law enforcement, the workplace, and schools. Despite widespread adoption of such techniques, limited knowledge exists regarding their valid use and interpretation among many who frequently perform these tests. This column discusses how obtaining a valid test result is a complex process because results are affected by several factors, including the substance of interest, test methodology, pharmacokinetics, chain-of-custody procedures, and intentional tampering.