Comparison of ADAMTS13 and Von Willebrand factor levels and activities, and plasminogen levels, in plasma products currently available for the treatment of thrombotic thrombocytopenic purpura in South Africa

Objective: Thrombotic thrombocytopenic purpura (TTP) results from a deficiency in the Von Willebrand factor (VWF) cleaving protease, ADAMTS13. Treatment involves plasma exchange (PEX) therapy with either fresh frozen plasma (i.FP), cryosupernatant (CSP) or solvent/detergent-treated plasma (SDP), available in South Africa as Bioplasma FDP. The aim of the study was to generate in vitro data on these products, and to explore possible differences between the products that may offer treatment advantages. Methods: Twenty samples per product (FFP, CSP and Bioplasma FDP) were analysed for levels and activities of ADAMTS13 and VWF. Plasminogen levels, a proposed physiological back-up system for ADAMTS13, were also determined. FFP and CSP samples were subanalysed according to ABO blood group. Samples were analysed by means of commercially available ELISA assays. Results: All samples had normal/high ADAMTS13 activity (Median activity for SDP = 94.0%, CSP = 80.5%, FFP = 122.0%) and plasminogen levels. The VWF content was mostly normal for Bioplasma FDP, typically deficient for CSP and mostly deficient for FFP, which was an unexpected finding. Depending on the parameter, Bioplasma FDP was the most standardised, with coefficients of variation (CV) from 14.1% to 27.3%, while FFP showed great inter-individual variation (CV 24.6% to 208.6%). Statistically significant differences were found across products (P <= 0.0095), and ABO blood groups (P = 0.0001). Conclusion: All three products can be used for the treatment of TTP. The choice of product depends on the need for additional viral safety, costs, product availability and the perceived impact of within-product variations.