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| Laboratory testing for patients on emicizumab: Case-based discussion and common challenges in monitoring Rajiv Pruthi. |
Abstract
Emicizumab is a bispecific antibody that is in clinical use for patients with hemophilia A with or without FVIII inhibitors. Its mechanism of action interferes with selected coagulation assays. Most importantly, interference with the one stage factor VIII assay and chromogenic assay with human reagents results in false normal or elevation of factor VIII activity. One effect is false negative factor VIII Bethesda titer assay results. Emicizumab does not interfere with the chromogenic factor VIII that use bovine reagents. Compliance with emicizumab treatment may be assessed with local APTT reagents, one stage factor VIII assay (with the factor VIII will be falsely elevated), or with performance of the emicizumab assay based on the modified one stage factor VIII assay. Anti drug antibodies are exceedingly rare. Determining the factor VIII equivalence with emicizumab therapy poses a challenge with current models. Individualizing emicizumab treatment based on thrombin generation assays requires optimization.
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