There’s a definitive article in the June, 2012 JTH that describes the three methods currently available to assay von Willebrand factor activity: ristocetin cofactor (VWF:RCo), collagen binding (VWF:CB), and a monoclonal antibody-based immunoassay (VWF:Act). See Favaloro EJ, Bonar R, Chapman K, Meiring M, Funk (Adcock) D. Differential sensitivity of von Willebrand factor (VWF) ‘activity’ assays to large and small VWF molecular weight forms: a cross-laboratory study comparing ristocetin cofactor, collagen-binding and mAb-based assays. J Thromb Haemost 2012;10: 1043–54. Based on this article, this month’s Quick Question asks which VWF activity assay method you use in your laboratory. Please check out the question at the right and select your answer.
Two additional words of explanation, these are the activity assays, the list does not include the standard VWF concentration immunoassay that is based on polyclonal antibodies, von Willebrand factor antigen (VWF:Ag) nor does it include the factor VIII (FVIIIC) activity assay. These are assumed to be part of every von Willebrand disease profile. Also, the ristocetin cofactor assay (VWF:RCo) is divided between the more traditional platelet aggregometry-based assay and the automated assay.
It may be that you use two VWF activity assays, for instance, you may run concurrent VWF:RCo and VWF:CB for confirmation and to detect subcategories. If so, please add a note of explanation using the Comments section of this post. Also, please post any additional qualifying comments or information you may consider.