Von Willebrand factor propeptide (VWFpp) — potential biomarker in inherited von Willebrand disease and acquired von Willebrand syndrome

Von Willebrand factor propeptide (VWFpp) is a fragment of a new synthesized VWF molecule that plays an important part in the biosynthesis of this protein. After completion of multimerisation of von Willebrand factor (VWF) dimers in the Golgi apparatus, as result of furin proteolysis VWFpp is truncated/disconnected from the mature VWF molecule to form a non-covalent complex with VWF. The VWFpp-VWF complex is stored in endothelial and platelet storage granules and released into the bloodstream where it dissociates into VWFpp and VWF. Plasma VWFpp level and ratio of plasma VWF propeptide (VWFpp) to VWF antigen (VWF:Ag) i.e VWFpp /VWF:Ag ratio are important biomarkers of VWF synthesis/release/clearance. These biomarkers have distinct therapeutic utility as they help to identify patients with von Willebrand disease (VWD) in whom DDAVP (desmopressin 1-desamino-8-D-arginine vasopressin) is ineffective due to rapid VWF clearance. They also have significant diagnostic value because they help to differentiate between congenital VWD subtypes as well as between congenital VWD and acquired von Willebrand Syndrome (AVWS). The purpose of the study was to determine the VWFpp level and the VWFpp/VWF: Ag ratio in patients with VWD and AVWS and to assess the significance of these biomarkers for diagnosis and management of congenital and acquired von Willebrand disease. Our study involved 120 VWD patients; 21 with AVWS and 111 healthy controls. Study results confirm that VWFpp level and the VWFpp/VWF: Ag ratio have significant value for discrimination between severe type 1 VWD and type 3 VWD as well as between acquired and congenital VWD which has serious implications for therapy. The biomarkers are also useful for identification of patients in whom DDAVP treatment may prove ineffective. In type 1 VWD (< 30 IU/ml) the VWFpp/VWF: Ag ratio was elevated in 57% of patients while in the group of patients with threshold VWF values (‘Low VWF’, 30–50 IU/dL) the ratio was within normal, which may be suggestive of other underlying causes of VWF deficiency. Assays in patients with non-neutralizing anti-VWF antibodies (AVWS) have shown that the VWFpp/VWF: Ag ratio can have significant impact on monitoring therapy and assessment of remission in patients with anti VWF antibodies.