Measuring factor VIII activity in patients with severe haemophilia A treated with extended half-life concentrates – comparison of selected assay results

Overview

Introduction: Optimal substitutional treatment includes measuring FVIII activity (FVIII: C) using the one-stage clotting assay (OSA) or chromogenic substrate assay (CSA). However, with the advent of FVIII concentrates with an extended half-life, discrepancies between methods have increased due to modifications of the FVIII molecule. Aim: Evaluation of OSA and CSA discrepancy in patients treated with extended half--life FVIII concentrates. Method: FVIII: C measurement by OSA with reagents Cephascreen® (Diagnostica Stago) and Pathromtin® SL (Siemens Healthineers) and by CSA BIOPHEN^TM FVIII: C (Hyphen BioMed) in patients treated with efmoroctocog alfa, rurioctocog alfa pegol, turoctocog alfa pegol and damoctocog alfa pegol. Results: The results of both methods correlated well for efmoroctocog alfa, the differences being up to 21%. The results of rurioctocog alfa pegol in the range of 15–200% were slightly lower using OSA with both reagents, on average by 11% and 18%, while the results up to 10% were higher using OSA with an average difference of 54% for Cephascreen® and up to 75% for Pathromtin® SL. The results of turoctocog alfa pegol were lower using OSA in the range of 15–200%, on average by 36% and 25%. The samples with FVIII: C above 10% of damoctocog alfa pegol were slightly higher using OSA (Cephascreen® by 18%), but samples up to 10% were significantly higher, with Cephascreen® on average by 91% and by 100% with Pathromtin® SL. Conclusions: OSA Cephascreen® or Pathromtin® SL and CSA Hyphen correlate excellently in the case of efmoroctocog alfa. Of the other concentrates, the results correlate excellently in the case of rurioctocog alfa pegol (only Cephascreen®) and damoctocog alfa pegol, and only for FVIII: C > 10%.

Keywords:

haemophilia A – FVIII activity – EHL concentrates