Evaluation of one-stage and chromogenic assays for the laboratory measurement of factor VIII activity following valoctocogene roxaparvovec infusion

Abstract

The article evaluates different assays for measuring factor VIII activity after the administration of valoctocogene roxaparvovec (VR), a gene therapy for severe hemophilia A. The study compares one-stage (OS) and chromogenic substrate (CS) assays and finds that CS assays provide consistent results across laboratories, while OS assays show significant differences compared to CS assays. The study suggests that using a CS assay is preferable for monitoring factor VIII activity over time. However, the study acknowledges limitations such as a small sample size and lack of consistency between laboratories. It recommends that laboratories without access to CS assays should send samples to a laboratory that does have access to CS assays for accurate measurement of factor VIII activity.