Adverse drug events in emergency department patients

Study objective: Adverse drug events (ADEs) have been studied in hospitalized patients. Less is known about this common type of injury in emergency department patients. This study seeks to measure the risks, incidence, severity, and costs of ADEs in an ED population. Methods: ED charts of visits to a university-affiliated tertiary-care ED occurring between March 1 and May 31, 1997, were retrospectively reviewed. The main outcome measures were ADE incidence, severity, and total cost. Visits identified by investigators as containing a suspected ADE were further assessed by using the Naranjo Adverse Drug Reaction (ADR) probability scale. Events judged as probable ADEs (Naranjo ADR probability scale score of >4) were compared with ED control visits best matched by age for disposition, survival, severity, payer, sex, race, age, number of drugs, and total cost. Results: Of 13,602 visits, 13,004 records were available. Three hundred twenty-one had suspected and 217 had probable ADEs (1.7% of evaluable encounters); these were compared with visits by 217 age-matched control patients. Insulin and warfarin were the most commonly responsible drugs. Patients with ADEs were older (mean age 45.1 versus 36.8 years; mean difference 8.3; 95% confidence interval [Cl] 3.7 to 12.9), were more often women (odds ratio [OR] 1.48; 95% Cl 1.01 to 2.16), took more drugs (mean number of drugs 4.1 versus 1.9; mean difference 2.2; 95% Cl 1.7 to 2.8), and were hospitalized more frequently (OR 2.29; 95% Cl 1.33 to 3.94) than control patients. Conclusion: ADEs encompassed an important segment of ED encounters and annual health care costs. ED screening may provide useful information about the epidemiology of outpatient ADEs.