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Variability in factor VIII concentrate measurement: results from SSC field collaborative studies
1Division of Haematology and Informatics Laboratory, National Institute for Biological Standards and Control, Potters Bar, UK. sraut@nibsc.ac.uk
Journal of Thrombosis and Haemostasis : JTH
|August 28, 2003
Summary
Collaborative studies on factor VIII concentrate potency revealed significant differences between one-stage and chromogenic assays, with varying results based on concentrate purity and predilution methods. Chromogenic assays and FVIII-deficient plasma predilution generally offered better interlaboratory variability.
Area of Science:
- Biochemistry
- Hematology
- Pharmaceutical Science
Background:
- Accurate measurement of factor VIII (FVIII) concentrate potency is crucial for effective hemophilia treatment.
- Existing methodologies and standards for FVIII potency assays can lead to interlaboratory variability.
- Understanding the impact of concentrate purity and assay conditions on potency results is essential for standardization.
Purpose of the Study:
- To compare FVIII concentrate potency measurements using routine local methodologies across multiple laboratories.
- To evaluate the influence of different FVIII concentrate purities and predilution methods on assay results.
- To assess interlaboratory variability in one-stage versus chromogenic FVIII assays.
Main Methods:
- Seven collaborative studies involving 12 different FVIII concentrates were conducted.
- Local routine methodologies, standards, and calculation methods were employed by participating laboratories.
- Potency was measured using both one-stage and chromogenic assays, with variations in predilution techniques (buffer vs. FVIII-deficient plasma).
Main Results:
- One-stage potencies were lower than chromogenic potencies for intermediate-purity and recombinant FVIII concentrates.
- One-stage potencies were higher than chromogenic potencies for high-purity FVIII concentrates.
- Interlaboratory variability (CVs) was generally greater for one-stage assays compared to chromogenic assays, especially for higher purity and recombinant concentrates. Predilution in FVIII-deficient plasma improved CVs for most concentrates.
Conclusions:
- Assay methodology, concentrate purity, and predilution techniques significantly impact FVIII potency measurements.
- Chromogenic assays and predilution with FVIII-deficient plasma are recommended for improved accuracy and reduced variability, aligning with international guidelines.
- Further standardization of FVIII potency assays is necessary to ensure consistent and reliable therapeutic product quality.