until further notice
SourceJournal of Thrombosis and Haemostasis, 9, 10, (2011), pp. 2003-8
Article / Letter to editor
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Laboratory of Hematology
Journal of Thrombosis and Haemostasis
SubjectNCEBP 14: Cardiovascular diseases
Summary. Background: The Bethesda and the Nijmegen assays are commonly used for the measurement of inhibitor levels in hemophilia A patients. Despite test innovations, the between-laboratory coefficient of variation (CVb) of factor VIII inhibitor test data in external quality surveys remains very high (40-60%) with a high degree of false-negative and false-positive results resulting in undesired effects on treatment. Objectives: Organization of a workshop in order to address the causes of this phenomenon and to suggest ways to improve the assays. Methods: Fifteen laboratories showing a high CVb in regular surveys and using a variety of methods participated in the wet workshop, which included four different sessions where variables probably contributing to the high CVb (e.g. use of [non-]buffered plasma, FVIII-deficient plasma, sample dilution and APTT reagents) were investigated. Results: The CVb varied from 30% to 70% in the first session of the workshop when the participants used their own test settings and reagents. The use of buffered normal pooled plasma and FVIII-deficient plasma as a reference sample by all participants did not significantly alter the CVb (35-50%) but decreased the number of false positives. However, the use of buffered pooled plasma in combination with standardized sample dilution procedures by all participants showed a significant improvement (CVb, 10-20%). Conclusions: These results may contribute to improvement of FVIII inhibitor testing. However, improved inter-laboratory comparison of factor VIII inhibitor assay results can only be reached when further local standardization is implemented.
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