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Background and Objectives: Platelet concentrates suspended in a platelet additive solution (PAS‐PC) are associated with a reduction in allergic response and are suitable for preparing pathogen‐inactivated PC. We aimed to develop an efficient platform for the dual preparation of PAS‐PC and platelet‐poor plasma. Materials and Methods: PAS‐PC was prepared in six steps by using a hollow‐fibre system based on cross‐flow filtration: priming, loading PC, loading PAS, collection of filtered liquid (flow‐through) and collection of platelets by washing with PAS followed by washing with air. In this study, the efficacy of platelet and plasma protein recovery and characteristics of recovered PAS‐PC and flow‐through plasma were analysed in detail. Results: Recoveries of platelet in PAS‐PC and plasma protein in the flow‐through were 95.4% ± 3.7% and 61.6% ± 5.0%, respectively. The residual plasma protein in PAS‐PC was 34.1% ± 2.8%. Although the expression level of CD62P, a platelet activation marker, in recovered platelets was approximately 1.2‐fold of that in original platelets, swirling patterns were well retained, and aggregation in PAS‐PC was not visible. Agonist‐induced aggregabilities, platelet morphology and hypotonic shock recovery were conserved. The patterns of plasma protein and lipoprotein in the flow‐through were comparable with those in the original PCs. The multimeric pattern analysis of VWF remained unaltered. Conclusion: We propose a highly efficient preparation system that enables the simultaneous production of PAS‐PC and platelet‐poor plasma. It also achieves a high recovery of functionally well‐retained platelets with very low activation. [ABSTRACT FROM AUTHOR]

BACKGROUND: ADAMTS13 specifically cleaves unusually large von Willebrand factor (VWF) multimers, which induce platelet thrombi formation under high shear stress. ADAMTS13 activity is deficient in patients with thrombotic thrombocytopenic purpura (TTP). The determination of plasma levels of ADAMTS13 activity is a prerequisite for a differential diagnosis of thrombotic microangiopathies. Here, a unique and highly sensitive enzyme immunoassay (EIA) of ADAMTS13 activity is described. STUDY DESIGN AND METHODS: ADAMTS13 hydrolyzes the peptide bond between Y1605 and M1606 of VWF. In this assay, a recombinant fusion protein (GST-VWF73-His) is used as a substrate. A panel of mouse monoclonal antibodies (MoAbs) that specifically recognizes Y1605, which is the C-terminal edge residue of the VWF-A2 domain and is generated by the enzymatic cleavage, has been produced. These antibodies were prepared with a synthetic decapeptide, termed N-10 (1596-DREQAPNLVY-1605), as the immunogen. Twenty-six clones specific to N10 were obtained, and one anti-N10 MoAb was used in this study. RESULTS: With horseradish peroxidase–conjugated anti-N10 MoAb, a standard enzyme assay was established. This assay was highly sensitive, and the detection limit was 0.5 percent of the normal. Further, an inhibitor of ADAMTS13 was measured to a level of 0.1 Bethesda units per mL. ADAMTS13 activity was measured in 20 patients with Upshaw-Schulman syndrome, a congenital TTP, and 61 acquired TTP patients. The activity measured by this assay and by the classic VWF multimer assay showed high correlation. CONCLUSION: A convenient and highly sensitive EIA for ADAMTS13 activity has been established. This assay can be introduced for routine laboratory work in transfusion medicine. [ABSTRACT FROM AUTHOR]