Usefulness of roadside urine drug screening in drivers suspected of driving under the influence of drugs (DUID).

In Belgium, the driving under the influence of drugs (DUID) procedure consists of three steps: observation of external signs of drug consumption by a police officer; an on-site urine test for amphetamines, cannabinoids, cocaine, and opiates; and blood sampling by a physician for gas chromatography-mass spectrometry analysis. The driver is sanctioned if THC is greater than 2 ng/mL, morphine is greater than 20 ng/mL, or amphetamine, methylenedioxymethamphetamine (MDMA), methylenedioxyethylamphetamine, N-methyl-1-(3.4-methylenedioxyphenyl)-2-butanamine, cocaine, or benzoylecgonine are greater than 50 ng/mL in plasma. We analyzed the results of 450 blood samples taken from May 2000 to February 2005. Cannabis was most often found above the cut-off (73.5% of the cases), followed by MDMA (20.4%), amphetamine (19.8%), benzoylecgonine (17.9%), cocaine (6.9%), and morphine (2.7%). One drug was found in 72.0% of the cases, two drugs in 22.6%, three drugs in 5.2%, and four drugs in 0.25%. In 10.7% of the plasma samples no target drugs were found above the legal cut-off. This percentage was 8.4% when urine was obtained and tested on-site and 21.2% when no urine was obtained (chi2 = 8.574, P = 0.0034). In 64.6% of these samples, a target drug (THC in 74.2%) was found under the legal cut-off. These data indicate that roadside urine testing significantly decreases the number of unnecessary blood analyses in DUID.