Validation of an enzyme immunoassay for detection and semiquantification of cannabinoids in oral fluid.
Oral fluid (OF) is gaining prominence as an alternative matrix for monitoring drugs of abuse in the workplace, criminal justice, and driving under the influence of drugs programs. It is important to characterize assay performance and limitations of screening techniques for Delta(9)-tetrahydrocannabinol (THC) in OF. We collected OF specimens by use of the Quantisal OF collection device from 13 daily cannabis users after controlled oral cannabinoid administration. All specimens were tested with the Immunalysis SweatOF THC Direct ELISA and confirmed by 2-dimensional GC-MS. The limit of detection was <1 microgL THC equivalent, and the assay demonstrated linearity from 1 to 50 microgL, with semiquantification to 200 microgL. Intraplate imprecision (n 7) ranged from 2.9% to 7.7% CV, and interplate imprecision (n 20) was 3.0%-9.1%. Cross-reactivities at 4 microgL were as follows 11-hydroxy-THC, 198% Delta(8)-tetrahydrocannabinol (Delta(8)-THC), 128% 11-nor-9-carboxy-THC (THCCOOH), 121% THC (target), 98% cannabinol, 87% THCCOOH-glucuronide, 11% THC-glucuronide, 10% and cannabidiol, 2.4%. Of 499 tested OF specimens, 52 confirmed positive (THC 2.0-290 microgL), with 100% diagnostic sensitivity at the proposed Substance Abuse and Mental Health Services Administration screening cutoff of 4 microgL cannabinoids and GC-MS cutoff of 2 microgL THC. Forty-seven specimens screened positive but were not confirmed by 2D-GC-MS, yielding 89.5% diagnostic specificity and 90.6% diagnostic efficiency. Thirty-one of 47 unconfirmed immunoassay positive specimens were from 1 individual and contained >400 ngL THCCOOH, potentially contributing to cross-reactivity. The Immunalysis SweatOF THC Direct ELISA is an effective screening procedure for detecting cannabinoids in OF.