Use of the collagen-binding assay for von Willebrand factor in the analysis of type 2M von Willebrand disease: a comparison with the ristocetin cofactor assay

Br J Haematol. 2002 Jan;116(1):187-92. doi: 10.1046/j.1365-2141.2002.03199.x.

Abstract

This study compares the utility of two functional assays for von Willebrand factor (VWF), the ristocetin cofactor assay (VWF:RCo) and the collagen-binding assay (VWF:CBA). We analysed a group of 32 patients with type 2 von Willebrand disease (VWD) (25 patients with type 2M, six with type 2A and one with type 2B) and 22 normal control subjects. VWF:RCo/VWF antigen (VWF:Ag) ratios and VWF:CBA/VWF:Ag ratios were compared between the patient and control groups. In the six patients with type 2A VWD, both VWF:RCo/VWF:Ag ratios and VWF:CBA/VWF:Ag ratios were discordant (< or = 0.7). In the 25 type 2M VWD patients, the VWF:CBA/VWF:Ag ratios were concordant (> 0.7), but the VWF:RCo/VWF:CBA ratios were discordant (< or = 0.7) (P = 0.001) compared with control subjects. Thus, VWF:RCo/VWF:Ag ratios were discordant in both type 2M and 2A VWD patient groups indicating a functional abnormality. However, VWF:CBA/VWF:Ag ratios were discordant in the type 2A VWD group but not in the type 2M VWD group. Our study showed that VWF:CBA is sensitive to functional variants associated with the loss of high-molecular-weight multimers, i.e. type 2A and 2B in VWD, but the assay was unable to discriminate defective platelet-binding VWD variants with normal multimeric patterns such as type 2M VWD. It was concluded that the VWF:CBA assay should be used in association with rather than as a replacement for the VWF:RCo assay.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Case-Control Studies
  • Collagen Type III / metabolism
  • Humans
  • Molecular Weight
  • Platelet Aggregation
  • Predictive Value of Tests
  • Protein Binding
  • Ristocetin
  • Statistics, Nonparametric
  • von Willebrand Diseases / classification*
  • von Willebrand Diseases / immunology
  • von Willebrand Factor / analysis*
  • von Willebrand Factor / immunology

Substances

  • Collagen Type III
  • von Willebrand Factor
  • Ristocetin