DRUGS - TOXICOLOGICAL SCREENING - urine

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Specimen: 20 mL urine (random specimen). If required for forensic or other official purposes, adequate standards of identification and security must be maintained and documented.

Method: Chromatography, mass spectrophotometry, immunoassay, “spot” tests. Official drug screening may require definitive identification of a drug, usually by GCMS.

Application: Detection of drug overdose. Identification of unauthorised taking of legal or illegal drugs by patients with suspicious clinical features. Screening for drug-taking in eg employees, sports competitors, drivers of vehicles involved in accidents. Monitoring of patient compliance with drug-free or methadone programme. See also FORENSIC TOXICOLOGY , LAXATIVES .

Interpretation: If the drug taken is known (eg paracetamol, salicylate, theophylline), measurement of plasma levels may be more appropriate. The presence of drug and/or metabolites indicates past drug taking. Urinary levels of drugs or metabolites vary with the drug involved, the time since the last dose, the dose taken and individual pharmacodynamics. Assay sensitivity depends on the analytical method, and some drugs are not excreted in urine or detected by certain assays. Consult pathologist.

Reference: Substance Abuse Testing Committee of AACC. Clin Chem 1988; 34: 605-632.

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