Most roadside tests for stoned driving in the United States currently involve a verbal assessment, and nothing equivalent to the Breathalyzer for alcohol exists yet for cannabis. A British company Oxtox has developed a disposable test for high driving, but is it good enough to see any use on the roadways?
Law enforcement agencies and public policy officials are scrambling for an answer to the cannabis sobriety test problem. The chemical properties of cannabis’ active ingredient, THC, differ considerably from those of alcohol, making it very difficult to design a Breathalyzer test for THC that’s as reliable as the one for alcohol. Blood or urine tests done in a laboratory are mostly infallible, but the search is on for a way to take that precision to a handheld device.
A reliable correlation exists between the blood alcohol level and the amount of ethanol a person emits from their breath. The Breathalyzer uses an electrochemical reaction that generates a current that it measures to extrapolate the drunkenness of a driver. This latest device by Oxtox also uses an electrochemical reaction to analyze THC in a person’s saliva. Trace amounts of THC react with a chemical to generate a current, and the whole process happens on a cheap, disposable screen-printed electrode. When put to the test, it only gave a 1% false positive rate (i.e. 99% specificity), but with a 28% sensitivity, the device only spots a smoker less than a third of the time, with 52% accuracy in the measurement.
Some authorities in Europe use DrugWipe to test suspects for a range of substances including cannabis using an immunoassay. DrugWipe, similar in appearance to a pregnancy test, also requires a small amount of a person’s saliva to react with a sensitive substance called an antibody impregnated on a strip of paper. Different antibodies are designed to react with different substances like MDMA, methamphetamine, THC, LSD, benzodiazapines, cocaine, etc. Some research indicates the DrugWipe can successfully determine if a person is under the influence of something, but conflicting results say it is only about 2/3 effective.
A product called Cannabix based in Vancouver has received some media attention lately, and has even received a $250,000 grant from the Colorado Office of Economic Development and International Trade. Cannabix apparently uses a breathalyzer-type design to capture microscopic mucus particles exhaled from the lungs and analyzes them for cannabinoids using a newly developed form of spectroscopy.
Another British company called Intelligent Fingerprinting has developed a device that can analyze the oils on a person’s fingerprint for drugs. Intelligent Fingerprinting also uses an immunoassay like DrugWipe, meaning it only gives a pass/fail answer. Though the device is marketed and distributed in the USA by Smartox, it does not yet have FDA approval, a requirement for government agencies to start using it.
Legal states have already set guidelines detailing how much THC is acceptable to be in person’s blood while driving. Low permissible limits for drivers of one to five nanograms of THC per liter of blood set high standards for developers of handheld devices. With so many companies clamoring for recognition from law enforcement agencies in the hopes of securing lucrative contracts to sell their devices, a winner is soon to emerge on top.
Photo Credit: Terry K. from Ontario
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