Drug-related admissions and hospital-acquired adverse drug events in Germany: a longitudinal analysis from 2003 to 2007 of ICD-10-coded routine data

BACKGROUND: Adverse reactions and medication errors are complications of drug use. Spontaneous reporting systems and pharmacoepidemiological studies incompletely detect the occurrence of these events in daily hospital care. In this study, the frequency and type of drug-related admissions and hospital-acquired adverse drug events (ADE) in Germany were assessed using routinely collected hospital data. METHODS: The study was based on aggregated hospital routine data covering the period 2003 to 2007 and annually recorded as part of the further development of the German Diagnosis-Related Groups. The 505 ICD-10-codes indicating an ADE were categorized in seven groups according to their certainty. Primary diagnoses were considered as a proxy for drug-related admissions, and secondary diagnoses as a proxy for hospital-acquired ADE. RESULTS: Among all hospital admissions, 5% were found to be at least possibly drug-induced and 0.7% very likely drug-induced. There was a significant increase in the overall rate of drug-related admissions over time (p < 0.038). Enterocolitis due to Clostridium difficile infection was the most frequent cause of a drug-related admission. About 4.5% of in-patients had experienced a hospital-acquired ADE. In addition, over the course of the study period, the overall frequency of hospital-acquired ADEs significantly increased (p < 0.001). CONCLUSIONS: In Germany, more than 5% of hospital episodes are either caused or complicated by an ADE. Between 2003 and 2007, there was a statistically significant increase in the overall rate and in some of the subcategories defined by the list of ICD-10-codes suspected to be indicative of an ADE. Before the use of routine data in pharmacovigilance and patient safety can be fully exploited, a further tailoring of both the ICD and the available variable set is needed.