Methylen Blue Photoinactivated Plasma vs Fresh Frozen Plasma in Thrombotic Thrombocytopenic Purpura Treatment: A Multicentric Prospective Cohort Study.

Plasma exchange (PE) with plasma infusion is the treatment of choice for Thrombotic Thrombocytopenic Purpura (TTP) but doubts remain as to whether all kinds of plasma are equally effective. Since October 2004, a multicentric prospective cohort study is being conducted in Spain to compare Methylene Blue Photoinactivated Plasma (MBPIP) with Fresh Frozen Plasma (FFP) in the treatment of TTP. Sixty-three first episodes of idiopathic TTP were included. MBPIP was used in 38 and FFP in 25. The treatment schedule consisted of daily PE (> 40 mL/kg of body weight) and costicosteroids (1.5 mg/kg/d). Response was defined as the achievement of a platelet count >= 150 x 109/L for at least three consecutive days, normal LDH level and absence of TTP-related symptoms and signs. Recurrence was defined as a fall in platelet count below 50 x 109/L or below 50% of the highest count achieved after response. Response lasting for more than 15 days was considered as remission. The prognostic significance of the kind of plasma used was investigated by logistic regression analysis after adjustment for other variables that had previously been found to influence on response to PE (gender; the Rock score; days from first medical attendance to PE; volume of plasma infused in the first 7 days of treatment). Both groups were comparable with regard to clinical and biological parameters at diagnosis. A severe deficit in ADAMTS13 activity was found in 9 out 12 (75%) patients treated with MBPIP and in 12 out of 16 (75%) patients treated with FFP. When compared to FFP, patients treated with MBPIP required a higher number of PEs (16±13 vs 9±7, p=0.004) and a larger volume of plasma (763±678 ml/kg vs 413±326 ml/kg, p=0.02) to achieve a remission and presented more recurrences while on PE treatment (21 out of 38 vs 6 out of 25, p=0.02). Splenectomy or rituximab was required in eight patients (21%) treated with MBPIP to achieve a remission vs in none out of the 25 patients treated with FFP (p= 0.02). After adjustment for other prognostic variables, patients in the MBPIP group had a lower likelihood of remission by the 8th treatment day (OR: 5.1; 95% CI: 1.6 – 15.9) and a higher risk of recurrence while on PE treatment (OR: 4.2; 95% CI: 1.3 – 13.5). In conclusion, MBPIP is less effective than FFP in the treatment of TTP.