Chromogenic factor VIII determination

The Chromogenic Bethesda Assay

Emicizumab interferes with the determination of the residual F VIII activity in the conventional one-stage Bethesda assay. Even after preliminary heat treatment emicizumab is not inactivated.

Coamatic F VIII is a chromogenic F VIII test whose components are of bovine origin. This makes the F VIII determination insensitive to emicizumab. The method of the Chromogenic Bethesda Assay (CBA) has been described and validated in 2 large studies.


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  1. Miller et al: "Characteristics of hemophilia patients with factor VIII inhibitors detected by prospective screening". Am J Hematol 2015 Oct;90(10):871-6
  2. Miller et al: "Comparison of clot-based, chromogenic and flourescence assays for measurement of factor VIII inhibitors in the US Hemophilia Inhibitor Research Study". J Thromb Haemost. 2013 Jul;11(7):1300-9

System of Haemostasis

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