Evaluation of the Benefits and Harms of Aspirin for Primary Prevention of Cardiovascular Events

Systematic reviews often assess the comparative effectiveness and safety of health care interventions. To be most useful to users, systematic reviews should include estimates of the potential benefits and harms that are important to decisionmakers. Quantitative approaches for the assessment of benefits and harms may enhance, support, and facilitate how decisionmakers use systematic reviews. Previously, we prepared a report on the challenges and principles of assessing benefits and harms of medical interventions, the influence of values and preference, and the key characteristics of quantitative approaches to benefit and harm assessment. That report identified 16 quantitative approaches for assessing benefits and harms. Researchers and methodologists developed several of these approaches using data from a single study, but these approaches could be used in systematic reviews. Reviewers from the Cochrane Collaboration have routinely used simpler approaches, such as the number needed to treat (NNT) and number needed to harm (NNH). Decisionmaking contexts that have a larger number of relevant benefit and harm outcomes may need more complex approaches. However, we have limited understanding of the comparative strengths and limitations of quantitative approaches to benefit and harm assessment because little work has been done to compare empirical applications of these approaches. The specific objectives of this report were: - To illustrate two quantitative approaches to benefit and harm assessment in the context of a systematic review; and - To evaluate the methodological challenges of applying the two quantitative approaches to benefit and harm assessment in a systematic review.