When von Willebrand disease is suspected, several specific assays can be performed, including the VWF antigen (VWF:Ag) assay, determination of Factor VIII procoagulant activity, and the VWF ristocetin cofactor (VWF:RCo) activity assay.
The latter entails studying the behaviour of healthy platelets, fixed with formaldehyde, in the presence of von Willebrand factor. Under these conditions, ristocetin activates VWF and gives rise to a platelet agglutination reaction.
The VWF:RCo and VWF:Ag assays can be combined, as part of the von Willebrand disease workup, to detect and distinguish between quantitative VWF deficiencies (types 1 and 3) and qualitative VWF deficiencies (type 2 except 2N).
The STA-VWF:RCo test developed by Stago is entirely automated on all analysers of the STA-R range.
*Availability depending upon the country