Drug Screening versus History in detection of substance use in ED Psychiatric Patients

Because self-reporting of substance use may not be reliable, physicians rely on drug screening. We tested the hypothesis that drug screening alone is sufficient to detect substance use in ED psychiatric patients. We prospectively evaluated patients receiving psychiatric consultation over 6 months ending in April 1998 in an urban medical/psychiatric ED with 42,000 annual visits. After informed consent, patients underwent a structured interview by trained research associates who queried regarding substance use in the past 3 days. This self-report was compared with urine drug screen results for 11 substances of abuse. Standard descriptive statistical techniques were used. Kappa statistics were used to assess concordance between history and drug screens. Two hundred eighteen patients participated, 124 had a urine drug screen obtained. Patients with and without urine drug screens were similar with respect to age (34.9 versus 34.9 years, P = .3) and psychiatric diagnosis (P = .24). Overall, there was only fair concordance between history and drug screens (kappa = 0.46). History alone detected substance use in 70 patients (57%); drug screening alone detected substance use in 77 patients (62%). The combination of history and drug screening more often detected substance use than either alone (90 pts (73%); P< .05 for both comparisons). Depending on the particular drug, there was wide variation in concordance between history and drug screen (kappaʹs varied from 0.07 for ethanol to 0.79 for cocaine). History was better than drug screening for ethanol use (40 versus 10 patients), and THC (28 versus 15 pts). Drug testing alone was never significantly better than history. Although self-reporting of substance use is not reliable, reliance on drug screening alone is also flawed. Optimal identification of drug use in emergency department psychiatric patients requires both history and drug screening.