Hair Tests Yield More Positive Results for Drug Use than Urine Tests

Drug tests that use hair samples turn up positive for cocaine and methamphetamine far more frequently than urine-based drug tests, USA Today reported Nov. 20.

Cocaine, for example, was detected in three out of every 1,000 urine tests that job applicants and employees took during the first part of 2009, but was found in 32 of every 1,000 hair tests — more than 10 times more frequently — according to Quest Diagnostics, a drug-testing firm.

Methamphetamine was detected in nine times more hair tests than urine tests, the company added. 

Hair tests can detect drug use during a three-month period, while the detection window for urine tests is only about three days, so the disparity in positive results is not surprising, experts said.

The Quest findings showed sharp declines in cocaine and mathamphetamine use in the workplace between 2005 and 2009.