title: Assessing cannabis consumption frequency: Is the combined use of free and glucuronidated THCCOOH blood levels of diagnostic utility?
abstract: Heavy cannabis consumption is considered incompatible with safe driving. In Swiss traffic policy, drivers suspected of regular cannabis use are therefore required to undergo medical assessment of their long-term fitness to drive. A whole blood concentration of the cannabis metabolite 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THCCOOH) of 40 µg/L is currently used by Swiss forensic experts as the decision limit for regular cannabis consumption. The present study aimed to investigate the suitability of THCCOOH-glucuronide blood levels as an additional and/or better marker for the frequency of cannabis use. Whole blood samples collected from 23 heavy (≥10 joints/month) and 25 occasional smokers (≥1 joint/month, but ≤ 1 joint/week) enrolled in a placebo-controlled cannabis smoking study were analyzed for THCCOOH and THCCOOH-glucuronide. Based on receiver operating characteristic (ROC) curve analysis, concentration thresholds could be established for distinguishing between these two groups. Proposed thresholds for heavy use were THCCOOH-glucuronide > 52 µg/L (100% specificity; 41% sensitivity) and/or total THCCOOH > 58 µg/L (100% specificity; 43% sensitivity). Optimum thresholds for occasional use were THCCOOH-glucuronide < 5 µg/L (73% specificity; 97% sensitivity) and/or total THCCOOH < 5 µg/L (62% specificity; 98% sensitivity). Our results indicate that the THCCOOH-glucuronide whole blood concentration is a useful parameter that complements the free THCCOOH level to assess the frequency of cannabis consumption. The consideration of the blood concentrations of both free and glucuronidated THCCOOH improves the identification of heavy users whose fitness to drive has to be carefully assessed. Copyright © 2016 John Wiley & Sons, Ltd.
authors.affiliation: Institute of Forensic Medicine, University of Bern, Bühlstrasse 20, 3012, Bern, Switzerland.
authors.forename: Marianne
authors.initials: M
authors.lastname: Hädener
authors.affiliation: Institute of Forensic Medicine, University of Bern, Bühlstrasse 20, 3012, Bern, Switzerland.
authors.forename: Marie
authors.initials: M
authors.lastname: Martin Fabritius
authors.affiliation: Institute of Forensic Medicine, University of Bern, Bühlstrasse 20, 3012, Bern, Switzerland.
authors.forename: Stefan
authors.initials: S
authors.lastname: König
authors.affiliation: Forensic Toxicology and Chemistry Unit, University Center of Legal Medicine, Chemin de la Vulliette 4, 1000, Lausanne 25, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Giroud
authors.affiliation: Institute of Forensic Medicine, University of Bern, Bühlstrasse 20, 3012, Bern, Switzerland.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Weinmann
mesh_terms: D000293:Adolescent; D000328:Adult; D000066448:Driving Under the Influence; D013759:Dronabinol / Q000031:analogs & derivatives* / Q000097:blood; D020719:Glucuronides / Q000097:blood*; D006801:Humans; D057230:Limit of Detection; D008297:Male; D008385:Marijuana Smoking / Q000097:blood*; D015990:Placebo Effect; D015813:Substance Abuse Detection / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods; D055815:Young Adult
chemical_list: D020719:Glucuronides; C016780:11-nor-delta(9)-tetrahydrocannabinol-9-carboxylic acid; D013759:Dronabinol
keywords: THCCOOH; THCCOOH-glucuronide; cannabis; consumption frequency; whole blood