THE COSTS OF ADVERSE DRUG EVENTS IN HOSPITALIZED-PATIENTS

Objective.-To assess the additional resource utilization associated wi th an adverse drug event (ADE). Design.-Nested case-control study with in a prospective cohort study, Participants.-The cohort included 4108 admissions to a stratified random sample of 11 medical and surgical un its in 2 tertiary-care hospitals over a 6-month period. Cases were pat ients with an ADE, and the control for each case was the patient on th e same unit as the case with the most similar pre-event length of stay . Main Outcome Measures.-Postevent length of stay and total costs. Met hods.-Incidents were detected by self-report stimulated by nurses and pharmacists and by daily chart review, and were classified as to wheth er they represented ADEs. Information on length of stay and charges wa s obtained from billing data, and costs were estimated by multiplying components of charges times hospital-specific ratios of costs to charg es. Results.-During the study period, there were 247 ADEs among 207 ad missions. After outliers and multiple episodes were excluded, there we re 190 ADEs, of which 60 were preventable. In paired regression analys es adjusting for multiple factors, including severity, comorbidity, an d case mix, the additional length of stay associated with an ADE was 2 .2 days (P=.04), and the increase in cost associated with an ADE was $ 3244 (P=.04). For preventable ADEs, the increases were 4.6 days in len gth of stay (P=.03) and $5857 in total cost (P=.07). After adjusting f or our sampling strategy, the estimated postevent costs attributable t o an ADE were $2595 for all ADEs and $4685 for preventable ADEs. Based on these costs and data about the incidence of ADEs, we estimate that the annual costs attributable to all ADEs and preventable ADEs for a 700-bed teaching hospital are $5.6 million and $2.8 million, respectiv ely. Conclusions.-The substantial costs of ADEs to hospitals justify i nvestment in efforts to prevent these events. Moreover, these estimate s are conservative because they do not include the costs of injuries t o patients or malpractice costs.