This paper studies the cross-reactivity of cannabinoid analogs in six urine immunoassay kits.
Six urine immunoassay kits (Abbott Cannabinoids—Abbott Diagnostics, LZI Cannabinoids (cTHC) Enzyme Immunoassay—Lin-Zhi International, DRI® Cannabinoid Assay and CEDIA™ THC—Thermo Fisher Scientific, ONLINE DAT Cannabinoid II—Roche Diagnostics and Syva EMIT®II Plus—Siemens Healthineers) were evaluated at two different cutoff concentrations: 50 ng/mL and 20 or 25 ng/mL, assay dependent. The six commercially available urine cannabinoid homogeneous immunoassay screening kits cross reacted with the following analogs: delta-8-THC, 11-OH-delta-8-THC, 11-COOH-delta-8-THC, 6-OH-CBD, 7-OH-CBD, all delta-10-THC and HHC carboxylic acid chiral analogs and olivetol with varying selectivity depending on the screening kit and cutoff concentration. The kits did not cross-react with the following analogs: CBD, 7-COOH-CBD, Abnormal CBD, CBDA-A and olivetolic acid. The analysis was performed on an Abbott Architect Plus c4000 (Abbott Diagnostics). Delta-8-THC, CBD, olivetol and their major metabolites, and delta-10-THC and HHC carboxylic acid chiral analogs were evaluated. The cross-reactivity was evaluated by preparing each analyte at 20, 50, 100 and 1,000 ng/mL in urine. Analytes that did not cross-react at 1,000 ng/mL for a cutoff were considered not detectable. If detected, the lowest concentration was used as the decision point to determine the precision at the immunoassay’s cutoff. There has been an exponential surge in the presence and use of cannabinoids since the federal legalization of hemp (Agricultural Improvement Act of 2018). This growth is attributed to delta-9-tetrahydrocannabinol (delta-9-THC) and cannabidiol (CBD), the most abundant phytocannabinoid components of cannabis and hemp, respectively, but with many other emerging THC analogs. Structurally, these analogs are similar to delta-9-THC, yet very little information is available about their potency and even less information is available regarding their detectability using commercially available cannabinoid screening kits. Due to their structural similarity, current cannabinoid homogeneous immunoassay screening methods may be able to detect these emerging cannabinoid analogs and their metabolites. (Published Abstract Provided)