Prevalence and nature of adverse drug events and the potential for their prevention - Population-based studies among adults

Prevalence and nature of adverse drug events and the potential for their prevention – Population-based studies among adults Katja M Hakkarainen, M.Sc.Pharm, Doctoral Student, Nordic School of Public Health NHV In the presentation, the methods and results of the doctoral thesis of Ms Hakkarainen (abstract below) will be presented and discussed. Background: Adverse drug events (ADEs) are among the most common adverse events in healthcare and a considerable public health concern. A large proportion of ADEs in hospitals and outpatient clinics are estimated preventable, but the preventability estimations vary and the burden of preventable ADEs is largely unknown in the general population. Aims: The overall aim of the thesis is to assess the prevalence and nature of ADEs in the general population and the potential for preventing ADEs. The specific objectives are to estimate the prevalence and preventability using physicians’ opinion, self-reports of the general public and medical records, and to investigate the nature of the identified ADEs, including sub-categories of ADEs. Other objectives are to estimate from previous literature the percentage of adult outpatients and inpatients with preventable adverse drug reactions (ADRs) and the preventability of ADRs; and to identify and systematically evaluate different methods for assessing the preventability of ADEs. Methods: An expert panel of Swedish physicians in 2010 (n=19), a population-based survey to Swedish adults in 2010 (n=7099), medical records of a random adult population sample in 2008 in a country council in Sweden (n=4995), and citations of bibliographic databases (n=5770) until 2010 were used as data sources. ADEs included ADRs, drug dependence and abuse, drug intoxications from overdose, sub-therapeutic effects of drug therapy, and morbidity due to drugrelated untreated indication. The physicians estimated the proportions of their current patients with ADEs and preventable ADEs, and the survey respondents reported experienced ADEs and their self-reported preventability during the past month. The three-month prevalence of ADEs and their preventability were assessed from the medical records manually in a stepwise manner. A metaanalysis and a systematic literature review were conducted to summarise previous studies on preventable ADRs and to methods to assess the preventability of ADEs. Results: Swedish physicians estimated that half of their current outpatients and inpatients experience ADEs, and almost one-fifth of the adult general public reported ADEs during the past month. The three-month prevalence of ADEs from medical records was 12%. Of sub-categories of ADEs, ADRs and sub-therapeutic effects were equally prevalent and constituted most ADEs. The nature of the sub-categories of ADEs differed in terms of associated drugs and affected organs. Based on the physicians’ opinion, self-reports and medical records, at least one-fifth of ADEs among the adult general public were potentially preventable, with higher preventability for serious ADEs. In previous literature, half of ADRs among hospitalised and emergency patients were preventable. The nature of preventable ADEs differed only moderately from all ADEs. Definitions and methods for assessing the preventability of ADEs were diverse, with unknown validity and scattered reliability. Conclusions: The findings of this thesis demonstrate that ADEs and potentially preventable ADEs are a considerable public health concern. Although serious ADEs in hospital and emergency care appear more preventable than all ADEs, the high prevalence of potentially preventable ADEs in the general population emphasises the importance of preventing ADEs in the entire health system. The results also highlight the need to improve the definitions, classification and assessment of preventable ADEs, to enhance developing strategies to prevent ADEs.