Urine Toxicology Screens in Drivers Suspected of Driving While Impaired from Drugs

Abstract

Objective: Police departments, in conjunction with the National Highway Traffic Safety Administration, have developed a standardized evaluation aimed at identifying drivers impaired by drugs other than ethanol. These evaluations are performed by specially trained police officers known as Drug Recognition Experts. Methods: We retrospectively reviewed the evaluations of 242 drivers detained for driving while impaired in the City and County of Denver from January 1, 1988 to June 30, 1990. Results: All drivers had urine toxicology screens performed, which were positive for a mean 1.2 ± 0.9 SD (range zero to four) for drugs having the potential for causing driving impairment. The 193/242 urine screens (79.8%) testing positive showed the following drugs: cannabis 162 (66.9%), stimulants (including cocaine metabolites) 80 (33.1 %), depressants (benzodiazepines and barbiturates) 24 (9.9%), narcotics 12 (5.0%), inhalants (toluene) 1 (0.4%), hallucinogens (LSD) 1 (0.4%), and other 3 (1.2%). Drug Recognition Experts, based on their initial evaluation, were able to predict correctly some or all of the drugs found on the urine screens in 178/242 (73.6%) of cases. Overall agreement between the Drug Recognition Experts opinions and urine screen results had a kappa value (p < 0.05) of 0.41. Conclusions: There was a high rate (79.8%) of positive urine toxicology screens in drivers suspected of nonethanol drug impairment. In most cases, Drug Recognition Experts were able to reliably predict the results of these screens.