Saliva test designed to identify marijuana

Marijuana warranted much media and political attention in recent years. Along with increased attention there has been increased consumption, in particular of edible marijuana.

Unlike other forms of the drug, consumption of edibles is particularly difficult to test for, which is incredibly problematic when it comes to identifying drivers impaired by the drug.

As the legalization of recreational and medical use of marijuana has increased, so too has its consumption. Almost one-third of all marijuana is now consumed in the food or drink form. Following increased usage has been an increase in marijuana-associated accidents.

Statistics show that the presence of tetrahydrocannabinol (THC), the main psychoactive constituent in marijuana, among weekend, nighttime drivers has increased from 8.6 percent in 2007 to 12.6 percent in 2013 and 2014.

Researchers from the National Institute on Drug Abuse may have solved the detection problem, however, with a new roadside saliva test. The test is designed to test for the presence of THC.

Saliva was chosen as the testing medium due to the failure of breath tests to identify THC accurately. Saliva offers just as fast of a solution, but until now had yet to be studied as a viable option.

The study, led by Marilyn Huestis, was published in the American Association for Clinical Chemistry’s (AACC) Clinical Chemistry journal.

During the study, frequent marijuana smokers were given brownies laced with exactly 50.6 mg of THC. Saliva and blood samples were collected regularly over the course of 48 hours and analyzed.

Two specific devices designed for roadside use were used to analyze the samples. The first, the Draeger DrugTest 5000 uses the THC cutoff of 5 ug/L and the second, the Alere DDS2 uses the cutoff 25 ug/L. Liquid chromatography-tandem mass spectrometry (a standard laboratory procedure used for marijuana testing) was used to analyze both the saliva and blood samples at THC cutoff points ranging from 0.2 ug/L to 25 ug/L.

From the various results, researchers were able to determine that cutoffs greater than or equal to 1 ug/L and greater than or equal to 2 ug/L led to the highest number of accurate results. Accuracy was determined by initially screening subjects before evaluating the results of the confirmation testing.

Ultimately, Heustis’ team was able to prove that while saliva testing devices need lower cutoff points to maximize accuracy, they are viable for roadside testing. While analyzing the samples, the team was also able to look at the effect of time on the concentration of THC in the saliva and blood.

Surprisingly, they found that blood and saliva concentrations did not correlate with one another and that saliva was found to be a more viable medium for roadside testing.

“For the first time, we compared performance of on-site oral fluid devices following controlled edible cannabis administration,” Huestis said, according to a press release. “A reliable conversion between blood and oral fluid THC concentrations does not exist [...] Therefore, we recommend oral fluid screening either with the DT5000 or DDS2 followed by oral fluid confirmation. Rapid and sensitive on-site oral fluid devices offer advantages for roadside drug screening, allowing trained officers to presumptively identify drug use, without lengthy delays associated with blood collection.”