Alterations of Factor VIII von Willebrand Factor in Clinical Conditions Associated with an Increase in its Plasma Concentration

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Abstract
Summary. Factor VIII-related antigen (VIIIR: Ag) was consistently higher than factor-VIII procoagulant activity (VIII:C) in 57 patients with clinical conditions characterized by acute-phase reactions. Two different methods for measuring VIII:C (one- and two-stage assays) and VIIIR: Ag (electroimmunodiffusion and immunoradiometric assay) gave concordant results in the majority of cases. In 43% of plasma samples, crossed immunoelectrophoresis in agarose gel was characterized by the appearance of an additional, fast-moving precipitin peak which was immunologically identical with the major, slower-moving VIIIR : Ag peak. The fast-moving peak was detected in all the patients with clinical conditions typically associated with increased plasma proteolysis (DIC, acute pancreatitis, during thrombolytic therapy). It was present in a smaller proportion of cases with liver and renal failure and malignancies and in the post-operative period. The additional VIIIR : Ag peak is thought to be the result of in vivo factor VIII/von Willebrand factor fragmentation by proteolytic enzymes.