United States Thrombotic Thrombocytopenic Purpura Apheresis Study Group (US TTP ASG): multicenter survey and retrospective analysis of current efficacy of therapeutic plasma exchange. Bandarenko N, Brecher ME. Journal of Clinical Apheresis 1998;13(3):133-141.

Thrombotic thrombocytopenic purpura (TTP) is still not completely understood from the perspective of its etiology, pathophysiology, and treatment. Once recognized, the accepted standard of care for TTP is daily therapeutic plasma exchange (TPE). However, the diversity in TPE treatment protocols has made comparisons of clinical research between institutions difficult. This study strived to assess the current practice of TPE in order to provide direction for prospective controlled clinical trials. Twenty large apheresis centers within the U.S. responded to a survey to establish the current status of TPE in TTP. A retrospective analysis from data provided by 14 of 20 centers included 115 initial presentations of primary TTP from 1994 through 1997. Ages ranged from 5 to 90 years (mean 47 years) with a female to male ratio of 2:1. These patients had an overall mortality rate of 10% and relapse rate of 37%. Of the 38 relapses, 25 were classified as exacerbations having occurred within two weeks of remission and discontinuation of daily TPE. The majority of deaths (58%) occurred within 48 hours of presentation. Variation in therapeutic targets (platelet count and serum LDH) and the number of plasma volumes exchanged per procedure did not affect the relapse rate. Initial platelet count and LDH were not predictive of mortality. Response, relapse, and mortality rates with the combination of 5% albumin for the initial 50% of TPE followed by plasma for the final 50% of TPE as replacement were comparable or possibly better than plasma-only replacement strategies. Forty percent of centers routinely used a TPE taper; however, there was no statistical difference in relapse rates comparing the taper and non-taper sub-groups. By controlling for adjunctive modalities such as steroids and antiplatelet agents, it is hoped that future prospective clinical trials may optimize the role of TPE in TTP, minimize patient exposure to blood products and procedures, shorten the clinical course of TTP, and reduce mortality. Early recognition and medical intervention remain the most important defense until more questions are answered.