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Laboratory approaches to drug testing in DUID cases , Immunoassay drug screening

المؤلف:  Sue Jickells , Adam Negrusz (Editors)

المصدر:  Clarkes Analytical Forensic Toxicology

الجزء والصفحة:  320

2026-10-28

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Laboratory approaches to drug testing in DUID cases

Immunoassay drug screening

Many different types of immunoassay screening tests are available commercially. The techniques in most widespread use include enzyme multi plied immunoassay technique (EMIT), enzyme linked immunosorbent assay (ELISA), kinetic interaction of microparticles in solution (KIMS) and fluorescence polarisation immunoassay (FPIA). Radioimmunoassay is also a suitable technique but is tending to be replaced in many laboratories for health and safety and environ mental reasons. When applied properly, any of these techniques is suitable for drug screening in DUID cases. Although the specificity of immunoassay tests have improved markedly, there is always the possibility of a false positive result, i.e. of the test showing a positive result even though no drug or metabolite is present in the test specimen. Hence immunoassays must be treated as a screening technique only, and should not be considered proof of the identification of a compound without a complementary confirmatory analysis. Additionally, since the sensitivity of the immunoassay panel is limited, and cross-reactivities within a class of drug vary widely, it may be necessary to conduct GC-MS analysis when a drug is indicated specifically (e.g. via symptoms seen in roadside sobriety tests; drug paraphernalia in the driver’s vehicle; odour of drugs noticed in the suspect’s vehicle when first stopped), even if the immunoassay result is negative.