Toxicological investigations for drugs of abuse in arrested drivers: A 2-year retrospective study (2005–2006) in Strasbourg, France

Driving under the influence of drugs of abuse (DRUID) is prosecuted in France since 2001. Biological controls are performed according to a 2-step procedure: urine immunoscreening followed, in case of positivity, by a blood analysis using a separative technique coupled to mass spectrometry. This paper presents a 2-year (2005–2006) retrospective review of blood analyses performed in this framework at the Medico-Legal Institute of Strasbourg, France. Over this period 611 subjects were controlled on request of the authorities. Of this population, 532 (87.1%) were male. Mean age was 31.7±14.4 years, 57.9% of subjects were in the range 15–29 and 31.1% in the range 20–24. On the 611 drivers, 296 (48.4%) were found positive for at least 1 drug using a preliminary blood immunoassay (ELISA). Among them, 254 were positive for cannabis, 81 for opiates, 22 for cocaine and 8 for amphetamine derivatives. Psychoactive medications were additionally tested in 278 drivers, and detected in 53 (19.1%). Benzodiazepines were the most frequently identified. On the 254 subjects tested positive for cannabis by ELISA, 202 had detectable levels of THC in blood (which is mandatory for engaging prosecution against the drivers). THC concentrations were in the range 0.1–49.9ng/ml. Our results clearly illustrate the huge prominence of cannabis among substances involved in DRUID. This study also highlights some pitfalls of the DRUID repression policy currently followed by France, especially interpretation of low concentrations of drugs of abuse (in our study, 28.2% of drivers found positive for cannabis at the immunoassay screening had blood THC levels<1ng/ml): since no minimum threshold for blood concentrations has been defined in our country the fate of arrested drivers is prone to vary depending on the sensitivity of techniques employed from one laboratory to another, which might contradict the principle of equality of citizens before the law.