Treatment policy should be based on all trial evidence, not subgroup analysis

EDITOR—We have suggested that aspirin for primary prevention is safe and worthwhile when the estimated 10 year coronary risk is >15%, provided that any hypertension is controlled.1 This conclusion comes from conservative interpretation of a meta-analysis examining the balance of benefit and risk in four large randomised controlled trials of aspirin for primary prevention, and fully supports recommendations in the Joint British Societies and British Hypertension Society guidelines.2 One assumption central to this analysis, and to these guidelines, is that relative risk reduction by aspirin is constant, so that the magnitude of benefit from aspirin is determined by pretreatment coronary risk.

Unfortunately, Meade et al did not examine this assumption in their subgroup analysis of the thrombosis prevention trial.3 Rather, they present subgroup analyses according to individual risk factors (systolic blood pressure, age, and cholesterol concentration). These analyses are not really …