THROMBOTIC THROMBOCYTOPENIC PURPURA - OUTCOME IN 24 PATIENTS WITH RENAL IMPAIRMENT TREATED WITH PLASMA-EXCHANGE

The Canadian Apheresis Study Group recently completed a randomized clinical trial involving 102 patients with thrombotic thrombocytopenic purpura (TTP), in which treatment with plasma infusion and treatment with plasma exchange were compared. Thirty-three other patients were ineligible or refused to be randomly assigned in the trial. Of the 33 patients, 24 were assessed as ineligible because they would be unable to tolerate the fluid input that would occur if they were randomly assigned to receive plasma infusion. All 24 patients had oliguria and elevated creatinine and/or blood urea nitrogen level. These 24 patients were treated with acetylsalicylic acid, dipyridamole, and plasma exchange according to the standardized protocol defined in the trial. Blood for tests of factors possibly involved in the pathogenesis of TTP was drawn before exchange and at intervals during and after exchange. The mean platelet count before exchange was 35.5 x 10(9) per L. In 12 of the 24 patients, the platelet count reached 150 x 10(9) per L or greater by 7 days after the initiation of plasma exchange. Three patients responded partially, in that their platelet count increased to at least twice that at presentation, but remained below 150 x 10(9) per L. One patient died during the first week. Of the eight other patients who experienced treatment failure at the 7-day assessment point, six subsequently responded, four while continuing to receive plasma exchange and two after plasma exchange had been discontinued. Of the 15 patients who either responded fully or responded partially by the end of the first cycle, all survived. A total of 4 of the 24 patients died, including the 1 patient who died during the first cycle of treatment. Thus, these patients, who had what some would consider to be the adult hemolytic uremic syndrome, did not differ in their response to plasma exchange from the patients in the randomized trial with less prominent renal dysfunction. The von Willebrand factor antigen level was elevated at presentation in patients who did and patients who did not respond, averaging 438 percent. The levels of several other circulating factors thought possibly to be related to the pathogenesis of TTP did not show consistent abnormalities and did not differ in patients who did or did not respond to plasma exchange.