A saliva-based test can reveal whether someone has consumed marijuana in the past 12 hours, and even provide the drug鈥檚 concentration levels, with results in less than 5 minutes.
The fast-acting cannabis test is less invasive and far faster than current gas chromatography mass spectrometry (GC-MS) tests that use blood or urine samples and can take several days to read. And unlike these other detection methods, the results focus only on recent consumption, meaning they can show whether a person is currently under the influence of the drug, says at Harvard University.
鈥淭here鈥檚 a growing concern about public safety with regard to cannabis use, especially for driving,鈥� says Lee. 鈥淔or alcohol, we already have a good test that can be done on the spot, but there is no [quick] test like that for marijuana.鈥�
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Lee and his colleagues developed a rapid test that uses an optical sensor to detect molecules of tetrahydrocannabinol (THC) 鈥� the main psychoactive component of cannabis 鈥� in saliva samples. It is known as the Express Probe for On-site Cannabis InHalation (EPOCH), and聽would theoretically cost about 拢3.60 to purchase once available on the commercial market, he says.
EPOCH uses a saliva-collection swab inserted into a free-standing, upright kit that mixes the saliva with THC antibodies and drips the mixture onto two tiny holes 鈥� one for testing and one as a control. The holes allow the sample to be perfectly placed in a sensor cartridge for the next step, which involves plugging the cartridge into a mobile telephone cradle. The docking site aligns the cartridge with a small LED light, a lens and the smartphone鈥檚 camera, which takes close-up shots of the sample to pick up optical signals when THC is present.
The researchers validated the accuracy of their test with the help of 43 cannabis users and 43 people, including 13 traditional tobacco smokers, who didn鈥檛 consume the drug. EPOCH had similar THC detection accuracy compared to GC-MS testing.
They found that the level of THC rapidly decreased for 6 to 12 hours after people smoked cannabis, but still remained higher than the legal limit for that period. Coffee, alcohol, tobacco and mouthwash use didn鈥檛 affect the results, he says.
The team has yet to test whether EPOCH can detect second-hand exposure to cannabis smoke like urine-based tests can.
Science Translational Medicine
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