Abstract Number: PB0835
Meeting: ISTH 2020 Congress
Background: Measurement of the clotting activity of Factor VIII (FVIII) can be done either by one-stage clotting (OSA) or by chromogenic substrate assay (CSA). Variability between these 2 methods has been known for several years, particularly for haemophilia A (HA) patients substituted with recombinant products or carrying specific genetic mutations. This variability can have major implications in terms of monitoring and diagnosis of HA and it is currently uncertain whether both assays should be used routinely.
Aims: This study emphasizes the need to use both assays in the management of the haemophilia patient.
Methods: In our institution, all FVIII assays (n=793) between 2015 and 2018 for diagnosis (endogenous FVIII) or monitoring (exogenous FVIII) were performed using both OSA (HemosIL Werfen kit) and CSA (Biophen FVIII:C HYPHEN BioMed). Discrepancy was defined as a twofold difference (ratio OSA/CSA >1.9 or < 0.6) and evaluated for the assay of exogenous FVIII (mainly severe HA patients substituted with standard half-life recombinant FVIII; n=287), mutated endogenous FVIII (male patients and haemophilia carriers of all severities; n=192) and non-mutated endogenous FVIII (healthy and VWD patients; n=268). Clinical discrepancy was defined as discrepant results leading to misclassification of HA patient according to the ISTH classification.
Results: For the assay of exogenous FVIII in treated HA patients we noticed 4.5% and 5.5% of discrepancies with higher CSA and OSA values respectively. For the assay of endogenous FVIII in untreated HA patients, a clearer trend was observed with 10.4% and 16.7% discrepancies with higher CSA and OSA respectively. For non-mutated endogenous FVIII, no significant discrepancy was noted. Considering clinical discrepancy, OSA misclassified 22% while CSA misclassified 17% of HA patients.
Conclusions: Discrepancies between CSA and OSA assays are frequent for both endogenous and exogenous FVIII. For the time being, both assays should ideally be routinely performed for diagnosis and monitoring of HA patients.
To cite this abstract in AMA style:Fauconnier C, van Dievoet M-, Lambert C, Defour J-, Eeckhoudt S, Hermans C. Discrepancies between FVIII Assays in Routine Diagnosis and Treatment Monitoring of Haemophilia A [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/discrepancies-between-fviii-assays-in-routine-diagnosis-and-treatment-monitoring-of-haemophilia-a/. Accessed January 23, 2022.
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