Dr. Rice raises two questions about our study, in which we demonstrated that splenectomy prevents further relapses in patients with relapsing thrombotic thrombocytopenic purpura. The first question is whether our observation of a significant reduction in the rate of relapses after splenectomy compared with before splenectomy represents a clinically relevant observation (as Dr. Rice suggests) or whether it reflects the natural history of the condition. Increasing evidence now indicates that about one third of patients who survive the initial episode will have at least one relapse. These relapses could be temporally clustered around the first episode (as Dr. Rice suggests) or might occur sporadically, suggesting that the patient has a tendency to develop the condition. To my knowledge, the only study addressing this issue has been the prospective Canadian study on thrombotic thrombocytopenic purpura and apheresis, in which Shumak and associates [1] showed that 36% of surviving patients with the condition will have relapse. This study showed no evidence that the relapses were clustered around the initial episode. Rather, they occurred 1 to 9 years after the initial episode. Our own data Figure 1 in our article) support these observations. Consequently, for both methodologic (statistical) and intuitive reasons, we believe that our observation-that splenectomy prevents relapses of thrombotic thrombocytopenic purpura-accurately reflects the result of this intervention on the natural history of this disorder.

I do not agree with Dr. Rice's comments about the benign nature of relapses of thrombotic thrombocytopenic purpura. At least one of our patients has had a cerebrovascular accident during the relapses, with resulting long-term neurologic impairment. But even if we had not observed such an unfortunate outcome, all of my patients who have undergone splenectomy and are now essentially relapse-free would state that the procedure was modest compared with ongoing and periodic unexpected relapses that are managed by plasma exchange therapy. The recent use of laparoscopic splenectomy (which minimizes morbidity and hospital stay) has, at least to me, made the choice even clearer.