Treatment of acquired Thrombotic Thrombocytopenic Purpura in the U.S. remains heterogeneous: Current and future points of clinical equipoise

Background: The purpose of this survey was to describe current practices in the U.S. for treatment of acquired Thrombotic Thrombocytopenic Purpura (TTP), compare these with prior U.S. and current Canadian practices, and identify areas of clinical equipoise. Study design and methods: A research team member administered the survey by telephone. Questions included an estimate of the annual patient volume treated, apheresis and medical therapy practices for acquired TTP. Results: 32 centers from 22 states were surveyed. ADAMTS13 activity is used for confirmation of the diagnosis of acquired TTP (97%). Most commonly, daily plasma exchange (therapeutic plasma exchange [TPE]) is initiated with plasma as replacement fluid (91%) at 1.0 Plasma Volume (72%) and stopped with a platelet count of 150 × 10⁹/L (66%), and then TPE is tapered off (69%). Compared with a U.S. survey from 1998, a greater proportion of centers use plasma exclusively as the replacement fluid exclusively (29/32 vs 2/14 in 1998; P <.0001) and taper TPE (22/32 vs 8/20 in 1998, P =.0499). Compared with Canadian survey in 2016, a greater proportion of U.S. centers use plasma over cryosupernatant (29/32 vs 2/13 CAG centers, P <.0001) and initiate TPE with 1.0 PV compared with 1.5 PV (23/32 vs 0/14 CAG centers, P <.0001). Corticosteroid use is common but not universal (U.S. and CAG) and use of rituximab heterogeneous. Conclusion: Treatment of acquired TTP in the U.S. remains heterogeneous. Points of clinical equipoise identified were PV exchanged (1.0 vs >1.0), tapering of TPE versus none, and rituximab use.