Article original / Original article Usage de stupéfiants au volant, bilan des résultats de deux laboratoires (CHRU Lille et IRCGN) Drug abuse and driving, assessment of the results from two laboratories (CHU Lille and IRCGN)

Objective: Retrospective study of the results of confirmatory analysis performed by two laboratories in order to verify the overall performance of the screening tests (calculation of the positive predictive value) and to avaluate the overall performance of roadside tests when they are found positive. Material and Methods: Data collection of GC- MS results for four major families of illicit substances, after urine or oral fluid screening tests, or in the case of no available screening data. Results: The illegal substance most frequently encountered in the tested drivers is cannabis, with a prevalence (among the analyzed samples) of 51% at the Lille University Hospital (458 confirmed cases out of 895) and 87% at the IRCGN (679 confirmed cases out of 779). At the Lille University Hospital amphetamines come second, with 6% prevalence among the analyzed samples (57 positives for 895 cases). The opiate family is found in 15 among 108 confirmation analyses at the IRCGN. Cases where the presence of morphine has been demonstrated remain difficult to interpret in regard to the use of street drugs because of confounding factors related to the administration of pain killers or the intake of licit opiates. Conclusion: Urine or oral fluid tests are therefore able to select drivers who have used narcotics before or while driving. Cannabis is the most frequently found substance, which is consistent with available data on consumption patterns in the general population.