Urinary excretion profiles of 11-nor-9-carboxy-delta9-tetrahydrocannabinol: a delta9-THCCOOH to creatinine ratio study.
Monitoring the major cannabinoid metabolite (delta9-THCCOOH) to creatinine ratio (M/C) has been used to predict new drug use. According to Huestis and Cone, the best accuracy (85.4%) for predicting new marijuana use was a ratio > or = 0.5 from two urine specimens collected at least 24 h apart. Manno et al. recommended an M/C ratio of > or = 1.5. Subjects with a history of chronic marijuana use were screened for cannabinoid use by immunoassay (50-ng/mL cutoff), and presumptive positives were confirmed by gas chromatography-mass spectrometry for delta9-THCCOOH (15-ng/mL cutoff). Creatinine was analyzed with a cutoff concentration of 25 mg/dL. The study objective was to apply the criteria from both groups of workers to determine if consecutive urine specimens (collected at least 24 h apart) positive for cannabinoids could be used to differentiate new marijuana use from the excretion of residual cannabinoid metabolite (delta9-THCCOOH) in an uncontrolled setting. Serial urine specimens (826) were collected from 26 individuals. Huestis and Cone and Manno et al. ratios indicated new drug use in 83% and 33% of serial urine specimens collected at least 24 h apart, respectively. Clinically, the Huestis and Cone ratio is recommended because of a lower false-negative rate (7.4%) than the Manno et al. false-negative rate (24%). In legal situations, we recommend using the Manno et al. ratio because of its lower false-positive rate (0.1%) as stated by Huestis and Cone.
Fraser
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Department of Pathology and Laboratory Medicine, Queen Elizabeth II Health Sciences Centre, Halifax, Nova Scotia, Canada. adfraser@is.dal.ca
Worth
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D002188:Cannabis / Q000378:metabolism*; D003401:Creatine / Q000652:urine*; D013759:Dronabinol / Q000652:urine*; D005189:False Positive Reactions; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007118:Immunoassay; D015813:Substance Abuse Detection / Q000379:methods*
D013759:Dronabinol; D003401:Creatine