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More on subgroup analyses in clinical trials.

To the Editor: With regard to the article by Wang et al. (Nov. 22 issue), it is increasingly recognized that subgroup analyses in clinical trials are sometimes misused and require appropriate presentation and cautious interpretation.1,2 However, we would recommend that one type of subgroup analysis (in large “positive” trials or metaanalyses) be performed more often. That is, from a prognostic model, one categorizes patients into several ordered risk groups and estimates the absolute risk reduction in each group. For instance, the Third Randomized Intervention Treatment of Angina (RITA-3) trial,3 involving patients with acute coronary syndromes, showed an overall reduction in the risk of myocardial infarction or death associated with an invasive strategy as compared with conservative management. Such a riskstratified subgroup analysis then usefully clarified that this benefit was mainly in patients at high risk for myocardial infarction or death. In general, such an approach can be an important aid for clinical practice, so that for any specific patient, one can judge the absolute benefit of a new treatment (set against the absolute risk of side effects, as well as costs if relevant) and decide whether the treatment is warranted for that patient. This approach is also applicable when, with regard to relative risk, there is no evidence of subgroup interactions with treatment. The question of whether prasugrel is preferable to clopidogrel in acute coronary syndromes4 is an interesting example; it may be that the absolute benefit of the reduced risk of ischemic events outweighs the increased risk of bleeding only for high-risk patients. Similarly, if the absolute risk of myocardial infarction due to rofecoxib (Vioxx) had been properly quantified in appropriate risk-stratified subgroup analyses, the benefits of pain relief and reduced gastrointestinal bleeding might have been more clearly seen to outweigh the low absolute risk of myocardial infarction in a substantial proportion of patients, thus permitting the continued prescription of rofecoxib with appropriately restrictive labeling.