Testing edible marijuana for driver impairment is the subject of new research published in AACC’s Clinical Chemistry. Although edible marijuana is becoming increasingly common there is little information on testing drivers following consumption. This study evaluated the performance of roadside saliva tests following consumption of edible tetrahydrocannabinol (THC). Researchers observed that consumption of marijuana edibles have expanded along with legalized medical and recreational use and about 1/3 of all marijuana is now either eaten or ingested in drinks. Marijuana-associated traffic accidents and fatalities have also increased in states where they have been legalized increasing in those states from 8.6% in 2007 to 12.6% in 20132014.
In the study researchers gave occasional and frequent marijuana smokers brownies laced with 50.6 mg of THC. Over the next 48 hours the researchers collected saliva and blood samples at several time points. Saliva samples were analyzed using the roadside screening devices , the Draeger Drug Test 5000 (DT5000) and Alere DDS2 (DDS2) that use a cutoff point of 5µg/L and 25µg/L respectively to determine someone who is positive or negative for marijuana use. These tests were then confirmed using a standard laboratory method for marijuana testing–the liquid chromatography-tandem mass spectrometry to analyze both the saliva and blood samples at different .THC cut off points ranging from 0.2µ/L to 25µg/L.
By comparing the roadside and the LC-MS/MS results, researchers determined that confirmation cutoffs for THC of >1 µg/L and 0.2 µg/L led to the greater number of true positives both through the initial and through confirmation testings. Thus, saliva testing devices can successfully detect THC after ingestion of edible marijuana. Researchers recommended confirming edible marijuana use with saliva tests instead of blood tests due to a lack of correlation between the blood and saliva testing over time.