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A HIGHLY-SENSITIVE PLASMA VON WILLEBRAND FACTOR (VWF):RISTOCETIN COFACTOR ACTIVITY ASSAY BY FLOW CYTOMETRY
Abstract number: O-W-064
Chen1 D., Pruthi1 R.K., Nichols1 W.L., Heit1 J.A., Owen2 W.G.
11Division of Hematopathology, Department of Laboratory Medicine and Pathology 22Department of Biochemistry/Molecular Biology, Mayo Clinic, Rochester, United States
How-to-cite Chen D, Pruthi RK, Nichols WL, Heit JA, Owen WG. A HIGHLY-SENSITIVE PLASMA VON WILLEBRAND FACTOR (VWF):RISTOCETIN COFACTOR ACTIVITY ASSAY BY FLOW CYTOMETRY. J Thromb Haemost 2007; 5 Supplement 2: O-W-064
Abstract
Introduction: Assays of plasma von Willebrand factor (VWF) ristocetin cofactor activity (VWF:RCo) are essential for the laboratory diagnosis of von Willebrand disease (VWD). However, current manual or automated VWF:RCo assay methods have relatively poor operating characteristics. Our goal was to develop and validate an accurate, sensitive and simple platelet-based VWF:RCo assay.
Methods: Using green or red fluorochrome-labeled, fixed normal platelets and normal or patient plasma, ristocetin-dependent platelet agglutination was detected by flow cytometry. VWF:RCo activity was assayed as the number of double-positive events (green and red) among all green or red events, relative to the calibrator plasma signal (6~150% or IU/dL), and reported as % or IU/dL. We tested plasma samples from normal donors (n=51) and known VWD patients (type 1, n=16; type 2, n=20) based on clinical history and levels of plasma VWF antigen (VWF:Ag), VWF:RCo activity (manual platelet aggregometry/agglutination assay), factor VIII activity and VWF multimer analysis.
Results: For normal donors and type 1 VWD patients, VWF:RCo activity by flow cytometry vs. manual platelet agglutination correlated closely (R2=0.74), and VWF:RCo/VWF:Ag ratios did not differ significantly. In contrast, the VWF:RCo/VWF:Ag ratios for type 2 subtypes were significantly lower using VWF:RCo by flow cytometry vs. manual platelet agglutination (P<0.0001), especially for type 2A patients.
Table:
| Assay | Normal n=51(19)* | Type 1 VWD n=16(16) | Type 2 VWD n=20(16) | 2A n=8(6) | 2B n=6(6) | 2M 6(4) |
|---|
| VWF:Ag | 124.1(126.8) | 56.4(56.4) | 74.0(83.8) | 76.9(89) | 81.5(81.5) | 62.7(79.3) |
| VWF:RCo | 125.5(127.9) | 50.1(49.6) | 16.4(44.5) | 9.3(34.3) | 16.3(49.7) | 26.2(52.0) |
| VWF:RCo/Ag Ratio | 0.97(1.0) | 0.88(0.95) | 0.25(0.52) | 0.11(0.40) | 0.29(0.62) | 0.39(0.56) |
| *Flow cytometry method (Manual platelet aggregometry/agglutination method). |
Conclusions: This new flow cytometry-based VWF:RCo assay is simple, accurate, specific and sensitive (particularly for type 2 VWD).
To cite this abstract use the following format:
Journal of Thrombosis and Haemostasis 2007; Volume 5, Supplement 2: abstract number
Session Details
| Date: |
01/08/2007
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| Time: |
00:00-00:00
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| Session name: |
XXIst ISTH Congress |
| Subject: |
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| Location: |
Oxford, UK |
| Presentation type: |
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