PB0147 - Evaluation of an ELISA-based Factor IX assay for use in severe haemophilia B management.

Sunday, June 23, 2024

13:45 – 14:45 ICT

Room: Exhibition Hall

Presenting Author(s)

Walter J. Janse Van Rensburg, PhD

Associate Professor
Human Molecular Biology Unit, School of Biomedical Sciences, Faculty of Health Sciences, University of the Free State, Bloemfontein, South Africa
Bloemfontein, Free State, South Africa

Co-Author(s)

CB

Chené Bester

Postgraduate student
Human Molecular Biology Unit, University of the Free State
Bloemfontein, Free State, South Africa
JK

Jean F. Kloppers

Medical Scientist
Department of Haematology and Cell Biology, University of the Free State
Bloemfontein, Free State, South Africa

Background: Accurate and sensitive evaluation of factor IX (FIX) concentrations has a central role in the management of people with haemophilia B. FIX assays can assist in the evaluation of treatment efficacy, with a small increase in FIX levels (>1–2% of normal) taken as potentially effective prophylaxis. The one-stage FIX assay is the gold standard globally. However, chromogenic assays have been recommended for FIX treatment monitoring. Unfortunately, a major limitation of the automated one-stage and chromogenic assays is the relatively high lower limit of detection of some of these assays. The ELISA-based FIX method has the potential to overcome this limitation.

Aims: Our study aimed to evaluate the accuracy of an ELISA FIX assay versus the one-stage assay in determining low levels of FIX in people with severe haemophilia B.

Methods: We recruited 17 people with severe haemophilia B. We determined the FIX levels using an automated one-stage assay and an ELISA-based method. The two assays were compared using the Student T-Test, with p< 0.05 taken as a significant difference.

Results: No significant difference (p = 0.256) was found between the two assays. However, 47% of the results (8/17) demonstrated an inter-assay discrepancy, defined by having a one-stage/ELISA ratio >2.0. For roughly 70% of participants, the ELISA results were equal or less than the one-stage results. However, for one participant the ELISA method determined the FIX level at near normal levels of 46.3 IU/dL. This level did not correlate clinically to the bleeding phenotype and history of this participant, with the one-stage level of < 0.4 IU/dL being a more accurate reflection of the phenotype. This discrepancy may be due to the ELIZA's inability to distinguish between functional and non-functional FIX proteins.

Conclusion(s): Taking the discrepancies into account, we believe that the ELISA method is currently not a useful tool in haemophilia B management.