On-site oral fluid Δ9-tetrahydrocannabinol (THC) screening after controlled smoked, vaporized, and oral cannabis administration

Increasing driving under the influence of cannabis cases is an important short-term consequence of cannabis legalization. On-site oral fluid (OF) testing devices provide advantages for roadside drug screening, because OF Δ9-tetrahydrocannabinol (THC) indicates more recent cannabis intake than urine, and it can be collected non-invasively by law enforcement personnel. THC presence in OF primarily results from oromucosal contamination during cannabis inhalation. To date, on-site OF devices were not investigated following edible cannabis. We evaluated sensitivity, specificity, and efficiency of the Drager DrugTest® 5000 [DT5000] and Alere™ DDS®2 [DDS2] at various OF THC confirmatory cutoffs following controlled smoked, vaporized, and edible cannabis in frequent and occasional smokers. Times of last positive (t last) were evaluated for each device, cutoff, and smoking group. At a 5 µg/L OF THC confirmation cutoff, overall performance criteria exceeded the recommended 80% for both devices. At lower THC confirmation cutoffs (1–2 µg/L), true positive results were maximized but sensitivity was <80%. When confirmation cutoffs were below manufacturers’ screening cutoffs (5 µg/L DT5000, 25 µg/L DDS2), false negative results increased. No differences in t last were observed for DT5000 between the three administration routes, but later t last times were observed after smoking compared to vaporization with DDS2. Frequent smokers had significantly later median t last (5 h) compared to occasional smokers (1.5–3.5 h) for all conditions. There were no true positive results at 44 and 50 h with the DT5000 and DDS2, respectively. OF screening followed by confirmatory OF analysis is an important strategy for investigations of driving under the influence of drugs, with these data improving interpretation of cannabinoid OF results.