The impact of serious adverse drug reactions: a population-based study of a decade of hospital admissions in New South Wales, Australia

Aims: Adverse drug reactions (ADRs) have major impacts on patients and the hospital system. Methods identifying ADRs from selected International Classification of Diseases–10th revision (ICD-10) diagnosis and external cause codes can be applied to population-level hospital admissions data, enabling the study of rare, yet serious ADRs. The present study aimed to use ICD10-based methods to identify four types of serious idiosyncratic ADRs in Australia, and to assess changes in incidence and their impact on length of stay (LOS), readmission and in-hospital mortality. Methods: The study used a census of hospital admission data from New South Wales between July 2000 and June 2012. Changes in incidence rates over time relative to a control group were estimated using log-linear regression. To assess impacts on LOS, readmission and mortality, each ADR case was matched with five controls, and cases were compared with controls via generalized linear models appropriate to each outcome. Results: The incidence of three ADR types showed a significant increase over time relative to controls, while the fourth type showed no evidence of change. All ADR types were significantly associated with an increase in LOS of between 22% and 328%. Significant increases in risk of readmission or death were only observed for some ADR types. Conclusions: Reducing the incidence of idiosyncratic ADRs is challenging. ICD10-based methods support population-level analyses that can provide important insights into the effects and changes in ADRs over time. This, combined with strategies related to both patient care and drug monitoring pre- and post-commercial release, provides ways forward.