Assessing Harms When Comparing Medical Interventions

Comparative Effectiveness Reviews (CERs) are systematic reviews that evaluate evidence on alternative interventions in order to help clinicians, policymakers, and patients make informed treatment choices. To generate balanced results and conclusions, it is important for CERs to address both benefits and harms. However, assessing harms can be difficult. Benefits have been accorded greater prominence when reporting trials, with little effort to balance assessments of benefits and harms. In addition, systematically reviewing evidence for all possible harms is often impractical, as interventions may be associated with dozens of potential adverse events. Furthermore, there are often important tradeoffs between increasing comprehensiveness and decreasing quality of harms data.Adequately assessing harms requires CER authors to consider a broad range of data sources. For that reason, they need to deal with important challenges, such as choosing which types of evidence to include, identifying studies of harms, assessing their quality, and summarizing and synthesizing data from different types of evidence.