Development of inhibitor antibodies interfering with the function of FVIII replacement products is one of the most significant complications in the treatment of haemophilia A. Here, Eleanor Foxton and Áine McCormick consider several approaches to assay standardisation and EQA performance.
The FVIII Nijmegen-Bethesda assay (NBA) is used to quantify factor VIII (FVIII) inhibitors in patients with congenital or acquired haemophilia A. In-house FVIII NBA using chromogenic FVIII measurement has given a consistent low bias in ECAT Foundation external quality assessment (EQA) exercises and quality control (QC) material, leading to a methodology review. The aim of this short study is to reduce low bias seen with in-house NBA and standardise methodology using a CE-marked kit.
Materials and methods
Two suitable commercial kits were identified: FVIII Inhibitor kit (Technoclone) and CRYOcheck Factor VIII Inhibitor kit (Precision BioLogic). Both were tested against an in-house method using comparison of patient samples and FVIII Inhibitor plasma (Technoclone). Local practice includes the use of a chromogenic assay (Biophen FVIII, Hyphen BioMed) to measure residual FVIII activity using the CS2100 coagulation analyser (Sysmex).
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