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Factor VIII/IX inhibitor testing practices in the United Kingdom: Results of a UKHCDO and UKNEQAS national survey

Batty, Paul; Riddell, Anne; Kitchen, Steve; Sardo Infirri, Sofia; Walker, Isobel; Woods, Tim; Jennings, Ian; (2021) Factor VIII/IX inhibitor testing practices in the United Kingdom: Results of a UKHCDO and UKNEQAS national survey. Haemophilia , 27 (3) pp. 490-499. 10.1111/hae.14158. Green open access

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Abstract

INTRODUCTION: Inhibitor formation is the greatest challenge facing persons with haemophilia treated with factor concentrates. The gold standard testing methodologies are the Nijmegen-Bethesda assay (NBA) for FVIII and Bethesda assay (BA) for FIX inhibitors, which are affected by pre-analytical and inter-laboratory variability. AIMS: To evaluate inhibitor testing methodology and assess correlation between self-reported and actual methodology. METHODS: Methodology was evaluated using a survey distributed alongside a UK National External Quality Assessment Service Blood Coagulation external quality assurance (EQA) exercise for FVIII and FIX inhibitor testing. RESULTS: Seventy four survey and EQA exercise responses were received (response rate 63.2%), with 50 paired survey/EQA results. 47.1% (33/70) reported using the NBA and 42.9% (30/70) the BA for FVIII inhibitor testing. Review of FVIII inhibitor assay methodology demonstrated discrepancy (self-reported to actual) in 64.3% (BA reporting) and 27.6% (NBA reporting). Pre-analytical heat treatment was used by 32.4%, most commonly 56°C for 30 minutes. Assay cut-offs of 0.1-1.0 BU/mL were reported. EQA samples (acquired FVIII and congenital FIX) demonstrated titres and coefficients of variation (CV) of 3.1 BU/mL (0.7-15.4 BU/mL; CV = 43%) and 18.0 BU/mL (0-117 BU/mL; CV = 33%), respectively. No significant assay or laboratory factors were found to explain this variance, which could have resulted in change in management for 6 patients (5 misclassified high-titre FVIII inhibitors and 1 false negative for a FIX inhibitor). CONCLUSIONS: Heterogeneity was seen at each stage of assay methodology. No assay-related factors were found to explain variation in inhibitor titres. Further standardization is required to improve inhibitor quantification to guide patient care.

Type: Article
Title: Factor VIII/IX inhibitor testing practices in the United Kingdom: Results of a UKHCDO and UKNEQAS national survey
Location: England
Open access status: An open access version is available from UCL Discovery
DOI: 10.1111/hae.14158
Publisher version: https://doi.org/10.1111/hae.14158
Language: English
Additional information: © 2021 The Authors. Haemophilia published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License (http://creativecommons.org/licenses/by-nc/4.0/).
Keywords: Bethesda, NEQAS, haemophilia, inhibitor, survey, Blood Coagulation Factor Inhibitors, Blood Coagulation Tests, Factor VIII, Hemophilia A, Humans, United Kingdom
UCL classification: UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Cancer Institute
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Cancer Institute > Research Department of Haematology
URI: https://discovery.ucl.ac.uk/id/eprint/10164080
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