Association of preventable adverse drug events with inpatients' length of stay—A propensity‐matched cohort study

Summary Purpose Using clinical administrative data (CAD) of inpatients, we aimed to identify ICD‐10 codes coding for potentially preventable inhospital adverse drug events (ADE) that affect the length of hospital stay (LOS) and thus patient well‐being and cost. Methods We retrospectively assessed CAD of all inpatient stays in 2012 of a German university hospital. Predefined ICD‐10 codes indicating ADE (ADE codes) were further specified based on expert ratings of the ADE mechanism and ADE preventability in clinical routine to particularly identify preventable inhospital ADE. In a propensity‐matched cohort design, we compared patients with one or more ADE codes to control patients with regard to differences in LOS for three situations: all cases with an ADE code, cases with an inhospital ADE code, and cases with a preventable inhospital ADE code. Results Out of 54 032 cases analysed, in 8.3% (N=4 462) at least one ADE code was present. Nine of 128 evaluated ADE codes were rated as preventable in clinical routine, relating to 220 inpatients (4.9% of all identified inpatients with at least one ADE code and 0.4% of the entire cohort, respectively). Out of 48 072 evaluable inpatients for propensity score matching, 7 938 controls without ADE code and 4 006 cases with ADE code were selected. In all three settings, cases showed prolonged LOS vs controls (delta 1.13 d; 0.88 d and 1.88 d, respectively), significantly exceeding the maximum LOS as defined for each Diagnosis‐Related Group. Conclusion Inpatients with ADE codes referring to inhospital, potentially preventable ADE exceeded the maximum hospital stay fully reimbursed by insurance companies, indicating unnecessary long and costly inpatient stays.