To the Editor.
—The article by Dr Oler et al1 on unstable angina found a 2.9% absolute reduction for the combined outcome of nonfatal MI or death with heparin and aspirin, accompanied by a 1.5% increase in major bleeding. The authors' conclusion, that "most patients with unstable angina should be treated with both aspirin and heparin," should be accompanied by several caveats.Among the 6 trials included, only 2 were double blinded and these found no treatment differences. As it has been previously established that unblinded randomized trials may be associated with increased effect sizes,2 the magnitude of the heparin treatment effect may be overestimated. Moreover, the clinical heterogeneity of unstable angina makes the formulation of all encompassing treatment options precarious, as highlighted by the paradoxical result that the trial with the greatest rate of adverse outcomes failed to show a difference between the 2 treatments.3 This heterogeneity has been