Testing for drugs (prescription or illegal) in biological fluids is useful in the management of potential overdose patients, as well as other clinical situations. Historically, the laboratory used simple chemistry, or spot tests, progressing to thin layer chromatography, laboratory-based immunoassays and specific chemical assays, gas chromatography/liquid chromatography coupled with mass spectrometry, and rapid test kits or Point of Care Test (POCT) devices. Modern toxicology laboratories in North America today still use immunoassays and specific chemistry tests, but sophisticated mass spectrometry systems and minimal sample pre-treatment methods are the gold standard in the opinion of toxicologists.