title: Evaluation of the radioimmunoassay for benzoylecgonine (a cocaine metabolite) in human urine.
abstract: The 125I-radioimmunoassay (RIA) for benzylecgonine (cocaine metabolite) in urine was evaluated by comparison with gas-liquid chromatography (GLC) and thin-layer chromatography (TLC) and the Enzyme-Multiplied Immunoassay Technique (EMIT). By RIA, a statistically significant concentration, 2 microng/liter, was observed for urinary benzoylecgonine. The coefficient of variation for the RIA was 2.58+/-0.38% inter-assay and 2.20+/-0.14% intraassay. There was cross-reactivity with cocaine (more reactive than benzoylecgonine) and other members of the tropane family of alkaloids. There was agreement between results by RIA and GLC in 95.5% of the samples, between RIA and TLC in 87.0%, and between RIA and EMIT in 84.5%. The percentage of true false-positives was 3.5% for the RIA in comparison to GLC, 8.8% in comparison to TLC, and 9.1% in comparison to EMIT. True false-negatives were insignificant (0 to 1.0%). GLC and RIA results correlated highly (phi=0.908). GLC, therefore, was the best comparison method for this evaluation study. RIA for benzoylecgonine is sensitive, reproducible, and reliable for the detection of cocaine in urine.
mesh_terms: D002849:Chromatography, Gas; D002855:Chromatography, Thin Layer; D003042:Cocaine / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000652:urine*; D003429:Cross Reactions; D005069:Evaluation Studies as Topic; D005188:False Negative Reactions; D005189:False Positive Reactions; D005410:Flame Ionization; D006801:Humans; D007124:Immunoenzyme Techniques; D011863:Radioimmunoassay
chemical_list: C005618:benzoylecgonine; D003042:Cocaine