Such testing is routinely used in clinical practice to rule out substance-induced disorders, confirm medication adherence, and identify substances in overdose situations.
Employers and judicial courts also perform such tests to screen for illicit drug use.
Urine is the most commonly obtained specimens for drug testing due to its noninvasive process and ease of collection.
Both a parent drug and its metabolites may be detected in urine specimens and are usually in higher concentrations than seen in blood or serum samples.
Drug detection times are longer in urine, from one day up to several weeks, than in blood or serum samples.
Two main types of urinary drug testing exist: screening and comfiirmatory tests
Initial drug test or screens are performed using immunoassay technology.
Immunoassays allow for a large number of specimen screens to be completed and provide relatively rapid results.
Immunoassays are available as: enzyme-multiplied immunoassay technique, enzyme-linked immunosorbent assay, and florescence polarization immunoassay.
Immunoassays are antibodies to detect the presence of drug metabolites or classes of drug metabolites in the urine.
Immunoassays can unfortunately detect substances with similar characteristics resulting in cross-reactivity and false positive results.