Influence of type of exchange fluid on survival in therapeutic apheresis for thrombotic thrombocytopenic purpura.

Thrombotic thrombocytopenic purpura (TTP) is a potentially lethal disease that may respond favorably to plasma infusion or therapeutic plasma exchange (TPE) with frozen plasma (FP) as the exchange fluid. Frozen plasma from which the cryo-precipitated fraction has been removed (cryopoor plasma, CP) has reportedly been useful in refractory cases in which a response to FP is not being observed. We report a retrospective analysis of all cases of TTP treated by TPE with either FP (1985-1989) or CP (1989-1993) as exchange fluid at a large tertiary care hospital between the years 1985 and 1993. A severity score index was compiled for each patient using the platelet count, mental status, hematocrit, and renal function at the time of diagnosis. Nineteen patients were treated with FP (group 1) and 18 patients with CP (group 2). Groups did not differ in age, gender, race, hematologic parameters, or severity scores. Patients treated with CP, however, had more plasma exchange (14 +/- 10 vs. 12 +/- 8, respectively) and more fluid exchanged than these treated with FP (50 L +/- 36 vs. 37 L +/- 40, respectively). Survival was 72% in the CP group and 47% in the FP group. Although a survival advantage for the use of CP as exchange fluid in the treatment of TTP is suggested by our observations, the retrospective nature of the study, lack of randomization, and sequential rather than concurrent use of FP and CP indicates caution in interpretation. The data do indicate, however, that use of CP is acceptable as the initial exchange fluid in TTP.