Buyer Beware: Pitfalls in Toxicology Laboratory Testing.

Urine drug screens are commonly used in various clinical settings and situations. Immunoassays are the most commonly available method of testing for urine drug screens in hospitals. Although convenient, immunoassays are prone to false positive and false negative results. It is important for the health care provider to understand the principles of the laboratory methods involved with urine drug screens as this will help guide appropriate result interpretation and therefore improve clinical care.