Costs of adverse drug events in German hospitals - a microcosting study.

Objective: In Germany, only limited data are available to quantify the attributable resource utilization associated with adverse drug events (ADEs). The aim of this study was twofold: first, to calculate the direct treatment costs associated with ADEs leading to hospitalization and, second, to derive the excess costs and extra hospital days attributable to ADEs of inpatient treatments in selected German hospitals. Methods: This was a retrospective and medical record-based study performed from the hospitals' perspective based on administrative accounting data from three hospitals (49,462 patients) in Germany. Total treatment costs ("analysis 1") and excess costs (i.e., incremental resource utilization) between patients suffering from an ADE and those without ADEs were calculated by means of a propensity score-based matching algorithm ("analysis 2"). Results: Mean treatment costs ("analysis 1") of ADEs leading to hospitalization (n = 564) were (sic)1,978 +/- 2,036 (range (sic)191-18,147; median (sic)1,446; (sic)843-2,480 [Q1-Q3]). In analysis 2, the mean costs of inpatients suffering from an ADE (n = 1,891) as a concomitant disease or complication ((sic)5,113 +/- 10,059; range (sic)179-246,288; median (sic)2,701; (sic)1,636-5,111 [Q1-Q3]) were significantly higher ((sic)970; P < 0.0001) than those of non-ADE inpatients ((sic)4,143 +/- 6,968; range (sic)154-148,479; median (sic)2,387; (sic)1,432-4,701 [Q1-Q3]). Mean inpatient length of stay of ADE patients (12.7 +/- 17.2 days) and non-ADE patients (9.8 +/- 11.6 days) differed by 2.9 days (P < 0.0001). A nationwide extrapolation resulted in annual total treatment costs of (sic)1.058 billion. Conclusions: This is one of the first administrative data-based analyses calculating the economic consequences of ADEs in Germany. Further efforts are necessary to improve pharmacotherapy and relieve health care payers of preventable treatment costs