Comparison of ADAMTS13 and Von Willebrand factor antigen levels and activities and plasminogen levels, in the currently available plasma products for the treatment of thrombotic thrombocytopenic purpura in South Africa
Thrombotic thrombocytopenic purpura results from a deficiency in the Von Willebrand factor cleaving protease, ADAMTS13. Treatment involves plasma exchange therapy with either fresh frozen plasma, cryosupernatant, or solvent/detergent-treated plasma (available locally as Bioplasma FDP®). The research aimed to generate in vitro data on these products, and to explore possible differences between them that may offer treatment advantages. Twenty samples per product were analysed for levels and activities of ADAMTS13 and Von Willebrand factor, and plasminogen levels (a proposed physiological backup system for ADAMTS13). Fresh frozen plasma and cryosupernatant samples were subanalysed according to ABO blood group. All samples had normal/high ADAMTS13 activity and plasminogen levels. Von Willebrand factor content was mostly normal for Bioplasma FDP®, typically deficient for cryosupernatant and mostly (unexpectedly) deficient for fresh frozen plasma. Depending on the parameter, Bioplasma FDP® was the most standardised (CV: 14.1% to 27.3%), whilst fresh frozen plasma showed great inter-individual variation (CV: 24.6% to 208.6%). Statistically significant differences were found across products (p values ≤ 0.0095) and ABO blood groups (p value: 0.0001). In conclusion, all three products can be used for treatment of thrombotic thrombocytopenic purpura. Product choice depends on the need for additional viral safety, costs, product availability and the perceived impact of within-product variations.