CRD Summary: This review concluded that the use of aspirin for the prevention of cardiac events needed to be weighed against an increase in major bleeds. There was no justification in advocating the routine use of aspirin. Despite some concerns, the analyses contained a large number of people and the results seemed consistent. The conservative conclusions were likely to be reliable.

CRD Commentary: The authors addressed a clear research question supported by appropriate inclusion criteria. The authors acknowledged that some primary prevention trials contained patients with a history of coronary events and, therefore, did not meet the inclusion criteria. The authors searched several relevant databases and made an attempt to locate unpublished data. It was unclear whether language restrictions were applied, so language bias may be present. The authors did not state whether study selection was conducted in duplicate, or whether the accuracy and integrity of the data used in the individual patient data analyses were checked or validated in any way. Therefore, error and bias can not be ruled out. Despite these concerns regarding the conduct of the review, the analyses contained a large number of people, the results were seemingly consistent and the conservative conclusions were likely to be reliable.