Urinary cannabinoids in monitoring abstinence in a drug abuse treatment program

Urine specimens from 162 adolescents entering a drug treatment program were tested for cannabinoids using a photometric immunoassay (EMITst) and thin-layer chromatography (TLC). The EMITst has a cutoff point of detection 25 ng/mL or less of 9-carboxy-tetrahydrocannabinol. When reported as positive, both tests appeared to be reliable. There were two false-positive EMITst results and three false-positive TLC results in the 67 urine specimens that did not contain cannabinoids. When reported as negative, however, the EMITst with its 100 ng/mL cutoff failed to detect almost 40% of all cannabinoid-positive specimens. Of the 65 chronic marijuana smokers in the present study who stated that they had smoked within two days of their admission into the treatment facility, 17 (26%) went undetected by the 100 ng/mL cutoff used by the EMITst method. In clinical settings such as drug treatment programs, tests for urinary cannabinoids should use a detection threshold at 20 ng/mL or less.