Patient risk factors for adverse drug events in hospitalized patients

Background: Adverse drug events (ADEs) are common in hospitalized patients, but few empirical data are available regarding the strength of patient ris k factors for ADEs. Methods: We performed a nested case-control study within a cohort that incl uded 4108 admissions to a stratified random sample of 11 medical and surgic al units in 2 tertiary care hospitals during a B-month period. Analyses wer e conducted on 2 levels: (1) using a limited set of variables available for all patients using computerized data available from 1 hospital and (2) usi ng a larger set of variables for the case patients and matched controls fro m both hospitals. Case patients were patients with an ADE, and the matched control for each case patient was the patient on the same unit as the case patient with the most similar preevent length of stay. Main outcome measure s were presence of an ADE, preventable ADE, or severe ADE. Results: In the cohort analysis, electrolyte concentrates (odds ratio [OR], 1.7), diuretics (OR, 1.7), and medical admission (OR, 1.6) were independen t correlates of ADEs. Independent correlates of preventable ADEs in the coh ort analysis were low platelet count (OR, 4.5), antidepressants (OR, 3.3), antihypertensive agents (OR, 2.9), medical admission (OR, 2.2), and electro lyte concentrates (OR, 2.1). In the case-control analysis, exposure to psyc hoactive drugs (OR, 2.1) was an independent correlate of an ADE, and use of cardiovascular drugs (OR, 2.4) was independently correlated with severe AD Es. For preventable ADEs, no independent predictors were retained after mul tivariate analysis. Conclusions: Adverse drug events occurred more frequently in sicker patient s who stayed in the hospital longer. However, after controlling for level o f care and preevent length of stay, few risk factors emerged. These results suggest that, rather than targeting ADE-prone individuals, prevention stra tegies should focus on improving medication systems.