Von Willebrand Disease (VWD)
Part 3: VWF Activity Assay
A New von Willebrand Factor Activity Assay and Testing Algorithm
Problems with VWF:RCo Assay
June 2011
Despite its vibrant history and the status of being considered as the reference method, VWF ristocetin cofactor activity assay is problematic. It is imprecise with an average coefficient variation of 20% to 30%, possibly due to diversity of the reagent donor platelets and complexity of platelet aggregation kinetics. It has suboptimal lower and higher detection limit. Currently, the lower detection limit of VWF ristocetin cofactor activity is 12.5 IU/dL. In addition, VWF ristocetin cofactor activity is very imprecise when VWF antigen is lower than 30 IU/dL or higher than 200 IU/dL. And finally, VWF ristocetin cofactor activity over antigen ratio at a cut off of 0.7 is generally insensitive for acquired VWF abnormality when there are subtle losses of the highest molecular weight multimers.
Problems with VWF:RCo Assay |
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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