Tuesday 21 August 2018

Expert says saliva is superior to urine when testing for marijuana

By Kaitlin Washburn


In the U.S., if a driver is high, law enforcement officials test blood and urine to figure out what drugs are in the person's system. Oregon police collect urine samples in impaired driving cases.

But one leading expert says there's a far better option.

Marilyn Huestis, the former chief of chemistry and drug metabolism for the National Institute on Drug Abuse, said testing saliva gives the most accurate results and can be collected on the side of the road to supplement physical tests of coordination.

"I believe that we should be documenting impairment, and then we should be using oral fluid," Huestis said. "It's noninvasive, doesn't require medical personnel to draw it, it doesn't require a person to be stuck by a needle."

The testing is done in two stages. An officer inserts a cotton swab into the driver's open mouth and gathers a sample, which is tested immediately with a device that can detect six to eight drug compounds. A second swab is taken to a lab where it is tested for many more drugs, Huestis said.

Huestis is critical of blood and urine testing because drugs dissipate from blood quickly and can remain in someone's urine long after they're no longer intoxicated, especially THC.

A daily cannabis user's urine can remain positive for weeks, if not months after last use. Saliva would reflect more recent drug use, Huestis said.

Huestis said other places, such as Australia and Europe, have been using the saliva test for years and have done much better than the United States at reducing drug-impaired driving.

Without accurate data on drug-impaired driving, she said, policies can't be created, campaigns can't educate people and funds can't be directed toward a remedy for this problem.

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