A Review of the Methods, Interpretation, and Limitations of the Urine Drug Screen

Toxicology screens are used to detect the presence of prescription, nonprescription, or illicit substances. These tests are used in emergency situations to detect intentional or accidental overdose, to monitor drug dependency, and to screen for medical or legal purposes. An initial immunoassay reports qualitative results based on established cut-off concentrations. As a screening test, the initial immunoassay is less sensitive and therefore must be interpreted in the context of confounding variables such as the testing method, the substance being screened, and patient-specific characteristics. Either gas chromatography or high-performance liquid chromatography can be used to confirm positive results.