Verification and Implementation of a Bovine Chromogenic Factor VIII Assay for Hemophilia A Patients on Emicizumab Therapy.

BACKROUND: Patients with hemophilia A can develop inhibitors to factor concentrates. Emicizumab, a nonfactor-based therapy, has efficacy despite inhibitors. FVIII activity assessment on emicizumab treatment requires a bovine chromogenic reagent such as TriniCHROM FVIII:C.

METHODS

FVIII levels were measured in 15 patients with and 35 without hemophilia and 10 patients on emicizumab therapy with a time-to-clot and the TriniCHROM FVIII:C reagents. FVIII inhibitor levels were also determined with both reagents.

RESULTS

Acceptable agreement of FVIII and FVIII inhibitor levels were obtained with the 2 reagents (R² = 0.92 and 0.96, respectively) in patients not exposed to emicizumab. The time-to-clot FVIII assay overestimated FVIII levels in patients on emicizumab therapy. The chromogenic FVIII assay delivered accurate endogenous FVIII levels in patients on emicizumab therapy.

CONCLUSIONS

The TriniCHROM FVIII:C assay is compatible with routine automated coagulation analysers and delivers accurate FVIII and FVIII inhibitor levels.