University of Texas at Dallas researchers have developed a hand-held rapid saliva test that can measure the level of THC, the major active component in marijuana, with 94% accuracy. The sensor could be used as a tool for law enforcement officers to test drivers believed to be impaired. The electrochemical sensor is more sensitive than over-the-counter tests, which typically detect THC but do not determine its concentration. “Our saliva test will tell you what the THC level is, which in medical cases can help determine an optimal dosing level. “Our saliva test will tell you what the THC level is, which in medical cases can help determine an optimal dosing level,” Prasad said.