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

VWF Laboratory Testing Strategy

June 2011

We then adopted a screening scheme to increase the accuracy and efficiency of VWD testing and at the same time decreased the testing volume of the laborious VWF ristocetin cofactor activity assay. Any sample that has less than 55 U/dL VWF antigen or latex activity, or less than 0.8 VWF latex activity over antigen ratio will be reflected for further VWF testing which includes VWF ristocetin cofactor activity and multimer analysis.

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VWF Laboratory Testing Strategy

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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?