A rapid, automated VWF ristocetin cofactor activity assay improves reliability in the diagnosis of Von Willebrand disease

Thromb Res. 2011 Apr;127(4):341-4. doi: 10.1016/j.thromres.2010.11.029. Epub 2010 Dec 24.


Introduction: The effective diagnosis and monitoring of Von Willebrand Disease (VWD) requires an accurate assessment of ristocetin co-factor activity (VWF:RCo). Current methodologies include automated platelet aggregometry and manual visual agglutination both of which are laborious to perform and notoriously subject to a high degree of inter and intra assay variation.

Methods and materials: We have evaluated an automated VWF:RCo assay (BC Von Willebrand Reagent, Siemens, Marberg, Germany) for use on the Sysmex CS2100i analyser (Milton Keynes, UK) and retrospectively compared the results with an in-house manual visual agglutination assay and VWF antigen (Siemens) in normal subjects and in 53 patients with various types of VWD and 23 patients following VWF therapeutic treatment.

Results: The intra and interassay CV was improved with the automated assay (2.3% and 3.8% respectively) compared to 7% with the manual VWF:RCo assay. Good correlation was found between the two assays (r=0.91) in 53 patients with VWD. The mean manual VWF:RCo was 0.25IU/ml and mean automated VWF:RCo was 0.27IU/ml. A comparable increase in VWF:RCo following treatment, mostly with Desmopressin, was found in 13 patients with type 1 VWD (mean 3.9 fold increase with manual VWF:RCo and 3.1 fold with the automated VWF:RCo). In 13 patients with type 2 or 3 VWD following treatment mostly with concentrate , a higher increase was found with the automated VWF:RCo assay than the manual assay (mean 11.9 fold manually and mean 20.3 automated).

Conclusion: The automated VWF:RCo assay shows enhanced precision and analysis time in this difficult and time consuming laboratory test and its introduction should greatly improve the reliability of VWF testing.

Publication types

  • Evaluation Study

MeSH terms

  • Blood Coagulation Tests / economics
  • Blood Coagulation Tests / methods
  • Blood Platelets / cytology
  • Deamino Arginine Vasopressin / therapeutic use
  • Hemostatics / therapeutic use
  • Humans
  • Platelet Aggregation
  • Platelet Function Tests / economics
  • Platelet Function Tests / methods
  • Ristocetin*
  • Time Factors
  • von Willebrand Diseases / blood*
  • von Willebrand Diseases / diagnosis*
  • von Willebrand Diseases / drug therapy
  • von Willebrand Factor*


  • Hemostatics
  • von Willebrand Factor
  • Ristocetin
  • Deamino Arginine Vasopressin