Von Willebrand Disease (VWD)
Part 3: VWF Activity Assay

History of VWF Ristocetin Cofactor Activity (VWF:RCo) Assay

June 2011

VWF activity assay is required to diagnose and correctly classify von Willebrand disease or acquired von Willebrand syndrome. VWF ristocetin cofactor activity assay is considered a reference method to assess VWF-platelet-binding activity. In 1971, Dr. Howard and Firkin first observed ristocetin-induced platelet aggregation, which was apparently defective in von Willebrand disease patients. 2 years later, Dr. Weiss developed the first VWF ristocetin cofactor activity assay. We validated this assay in 1975 and have performed this assay as part of our VWD panel for the past 35 years. In the last year, we performed about 10 thousand VWF ristocetin cofactor activity assays with the majority of samples from Mayo Medical Laboratories.

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History of VWF:RCo Assay

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Jump to section:

• Introduction
• Objectives
• History of VWF Ristocetin Cofactor Activity (VWF:RCo) Assay
• Problems with VWF:RCo Assay
• Summary of External Quality Assessment of VWF:RCo
• von Willebrand Disease(VWD) Diagnostic Error Rates Due to Erroneous VWF:RCo Results⁵
• VWF:RCo/Ag Ratio is Insensitive for Aquired von Willebrand Abnormalities (AVWA)
• VWF:RCo is Inadequate for Detecting AVW Abnormality
• The New Automated VWF Activity by Latex-Immunoturbidity Assay (VWF:Lx)
• VWF Activity Assay by an A1 Domain Conformation-Sensitive Antibody⁶
• Performance Characteristics of VWF:Lx
• VWF:Lx and VWF:RCo Method Comparison
• VWF:Lx and VWF:RCo Bias Analysis
• Sample Categorization
• Comparison of VWF:Lx/Ag and VWF:RCo/Ag Ratios
• VWF:Lx and VWF:RCo Errors
• Severe Type 1 vs 2M⁷
• VWF:Lx and RCo Errors
• VWF:Lx/Ag is Sensitive to AVWA with Subtle Loss of Highest HMWM
• ROC Analysis of VWF:Lx/Ag and VWF:RCo/Ag for Detecting AVWA with Loss of HMWMs
• VWF:Lx/Ag vs VWF:RCo/Ag Ratios
• VWF Laboratory Testing Strategy
• Sensitivity and Specificity of the Screening Panel
• von Willebrand Disease Profile
• von Willebrand Disease Profile
• von Willebrand Disease Profile
• von Willebrand Disease Profile
• Limitations of VWF:Lx
• Summary
• References
• Questions?