Von Willebrand Disease (VWD)
Part 3: VWF Activity Assay
A New von Willebrand Factor Activity Assay and Testing Algorithm
Comparison of VWF:Lx/Ag and VWF:RCo/Ag Ratios
June 2011
Let us look at the distribution of the VWF latex activity over antigen ratio in different sample categories. The normal cut off is 0.7 as indicated by the red line. A vast majority of the normal samples had normal VWF latex over antigen ratios with rare outliers. All 57 type 1 von Willebrand disease samples had normal VWF latex activity ratios.
Twenty-eight of the thirty-one type 2A or 2B samples had abnormal ratios with only 3 outliers. All 4 2M VWD samples had abnormal ratios. We can not really compare the 2 methods in the group of severe types 1 vs 2M when VWF ristocetin cofactor activity is below lower detection limit. Finally, and interestingly, of the 24 samples with subtle losses of the highest molecular weight multimers, VWF latex activity ratios were significantly lower than those of the VWF ristocetin cofactor activity, and subsequently more sensitive for detecting such an acquired VWF abnormality. Occasional discrepant VWF ristocetin cofactor activity over antigen ratios were also observed.
Comparison of Ratios |
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?
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