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

VWF:Lx and VWF:RCo Errors

June 2011

Now let us examine the outliers in detail. 2 of the 3 samples of the normal group and type 2A or 2B group were lipemic. As we know that lipemia could potentially interfere with the optical property of a turbidimetric assay. However, the discrepancy of the remaining 1 sample from the normal and the 1 sample from the type 2A or 2B group can not be clinically verified since they were both Mayo Medical Laboratories samples. This underscores a potential limitation of this assay that it is still uncertain if the new assay will detect all type 2 von Willebrand disease variants, or conversely, if the new assay will pick up new type 2 von Willebrand variants that would have been missed by the VWF ristocetin cofactor activity assay. As for the group of severe types 1 or 2M, we classify the 8 samples by using a highly sensitive flow cytometric method.

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VWF:Lx and VWF:RCo Errors

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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?