Evaluation of immunoassay methods for detection, in urine, of drugs subject to abuse.

Results for abused drugs in urine, as obtained by radioimmunoassay (RIA), the “Enzyme Multiplied Immunoassay Technique” (“EM IT”), and hemagglutination inhibition (HI), were compared with each other, with fluorimetry, and with thin-layer chromatography (TLC). The immunoassays and fluorimetric methods were highly sensitive (30 tg/liter to 2 mg/ liter). Cross-reactivity (lack of specificity) varied with the method tested and the drug, ranging from no reaction to one exceeding that of the assay drug. The percentage of false positives for the immunoassays in comparison to TLC ranged from 3 to 31. The practical level of sensitivity for TLC, however, was only 1-5 mg/liter. False negatives were less than 2%. With the EMIT system (for those drug assays for which it is used), the total percentage of false values (negative and positive) ranged from 5 to 13. All the immunoassays were reliable within the limitations of the assay, relatively easy to use, did not require sample treatment, and several hundred samples could be analyzed during an 8-h period; but the cost was moderate to high, depending upon assay or sample volume. Judicious use of immunochemistry, spectrofluorimetry, and thin-layer chromatography to the detection of psychoactive drugs in urine permits rapid, reliable, and effective surveillance of drug use or abuse.