Comparative results with five cannabinoid immunoassay systems at the screening threshold of 100 micrograms/L

Five commercially available immunoassay techniques were compared for the detection of cannabinoid metabolites in urine at a positive cutoff of 100 micrograms/L. Numerical values, available for four of these techniques, were used to evaluate inter-assay equivalence at this threshold. The total number of positive results differed for each assay, with some individual samples exhibiting wide variations in numerical values. As a group, the radioimmunoassay systems gave a greater proportion of positive specimens than did enzyme-linked or fluorescence-polarization-based techniques. The single threshold of detection suggested by federal guidelines does not provide for equivalent screening of cannabinoids with these immunoassay techniques.