Standardization of von Willebrand factor propeptide: Value assignment to the WHO 6th IS Factor VIII/von Willebrand factor, plasma (07/316)

摘要

The ratio of von Willebrand factor propeptide (VWFpp) to VWF antigen (VWF:Ag) in plasma has been used to identify conditions associated with decreased half-life of VWF (e.g. type 1 von Willebrand disease with increased clearance, and acquired von Willebrand syndrome) [1-3]. Although there is an established international unit (IU) for VWF:Ag, currently assigned to the WHO 6th IS Factor VIII/VWF Plasma (07/316), there is no IU for VWFpp. Laboratories therefore rely on local or 'unofficial' reference preparations for VWFpp estimation, primarily comprising plasma pools with arbitrary 'plasma-based' units. This situation has the potential for considerable inter-laboratory variability as well as problems of continuity when local references are replaced. The present study was undertaken to assess the inter-laboratory variability of VWFpp (and VWF:Ag) estimates and to assign a value for VWFpp to the WHO 6th IS Factor VIII/VWF Plasma (WHO IS Plasma). Assignment of a value to the WHO IS Plasma will provide long-term continuity for the VWFpp unit and should lead to improved agreement between laboratories by providing a traceable route for the calibration of all local reference preparations.