Validation of an ELISA Synthetic Cannabinoids Urine Assay.

Abstract

Synthetic cannabinoids are touted as legal alternatives to cannabis, at least when first released, and routine urine cannabinoid screening methods do not detect these novel psychoactive substances. Synthetic cannabinoids are widely available, are a major public health and safety problem, and a difficult challenge for drug-testing laboratories. We evaluated performance of the National Medical Services (NMS) JWH-018 direct enzyme-linked immunosorbent assay (ELISA) kit to sensitively, selectively, and rapidly screen urinary synthetic cannabinoids. The NMS ELISA kit targeting the JWH-018 N-(5-hydroxypentyl) metabolite was used to screen 2492 urine samples with 5 and 10 mcg/L cutoffs. A fully validated liquid chromatography-tandem mass spectrometry method for 29 synthetic cannabinoids markers confirmed all presumptive positive and negative results. Performance challenges at ±25% and ±50% of cutoffs determined intraplate and interplate imprecision around proposed cutoffs. The immunoassay was linear from 1 to 500 mcg/L with intraplate and interplate imprecision of ≤8.2% and <14.0%, respectively. No interferences were present from 93 common drugs of abuse, metabolites, coadministered drugs, over-the-counter medications, or structurally similar compounds, and 19 of 73 individual synthetic cannabinoids (26%) exhibited moderate to high cross-reactivity to JWH-018 N-(5-hydroxypentyl) metabolite. Sensitivity, specificity, and efficiency results were 83.7%, 99.4%, and 97.6%, as well as 71.6%, 99.7%, and 96.4% with the 5 and 10 mcg/L urine cutoffs, respectively. This high throughput immunoassay exhibited good diagnostic efficiency and documented that the NMS JWH-018 direct ELISA is a viable method for screening synthetic cannabinoids in urine targeting the JWH-018 N-(5-hydroxypentyl) and related analytes. Optimal performance was achieved with a matrix-matched 5 mcg/L urine cutoff.