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von Willebrand factor standards for plasma and concentrate testing
1Division of Haematology, National Institute for Biological Standards & Control, Potters Bar, United Kingdom. thubbard@nibsc.ac.uk
Seminars in Thrombosis and Hemostasis
|July 25, 2006
Summary
Standardizing von Willebrand factor (vWF) measurements is crucial for both diagnosis and treatment. This study calibrated international standards for vWF:antigen and activity, improving consistency in therapeutic concentrate potency labeling.
Area of Science:
- Hematology
- Clinical Chemistry
- Biotechnology
Background:
- Plasma von Willebrand factor (vWF) exhibits wide-ranging levels in healthy individuals, making it suitable for international standardization.
- Accurate calibration of vWF International Standards (IS) is essential for consistent diagnostic and therapeutic applications.
- Existing standards address the need for continuity between plasma-derived and freeze-dried vWF preparations.
Purpose of the Study:
- To calibrate the World Health Organization (WHO) International Standards for plasma and concentrate of von Willebrand factor (vWF).
- To ensure consistency in the International Unit (IU) definition for vWF:antigen (vWF:Ag), vWF:ristocetin cofactor activity (vWF:RCo), and vWF:collagen-binding activity (vWF:CB).
- To maintain equivalence between vWF measurements for diagnosis (plasma) and potency labeling of therapeutic concentrates.
Main Methods:
- Calibration of WHO IS Plasma for vWF:Ag, vWF:RCo, and vWF:CB.
- Calibration of the WHO 1st IS vWF Concentrate for vWF:Ag and vWF:RCo against the WHO IS Plasma.
- Assessment of interlaboratory and intermethod variability for vWF:CB calibration.
Main Results:
- Calibration of WHO IS Plasma and Concentrate for vWF:Ag and vWF:RCo was successfully achieved, ensuring continuity of the International Unit (IU).
- Calibration for vWF:CB in the WHO IS Concentrate was not feasible due to significant interlaboratory and intermethod discrepancies.
- Evidence suggests the use of the WHO IS Concentrate reduces interlaboratory variability in vWF estimates for therapeutic concentrates.
Conclusions:
- The calibration of WHO IS Plasma and Concentrate for vWF:Ag and vWF:RCo supports accurate vWF quantification in clinical diagnostics and therapeutic concentrate potency.
- Addressing discrepancies in vWF:CB assays is necessary for complete standardization, potentially requiring standardized methodologies.
- Adherence to the "assay like versus like" principle and the use of WHO IS Concentrate are recommended to minimize variability in vWF measurements.