What is the role of inhibitors testing in the diagnosis of hemophilia A?

Updated: Apr 08, 2020
  • Author: Douglass A Drelich, MD; Chief Editor: Srikanth Nagalla, MBBS, MS, FACP  more...
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Testing for inhibitors is indicated when bleeding is not controlled after infusion of adequate amounts of factor concentrate during a bleeding episode. The presence of inhibitors is indicated by failure of correction of clotting times with 1:1 mix with normal plasma. Inhibitor concentration is titrated using the Bethesda method, as follows:

  • Positive result: ≥ 0.6 Bethesda units (BU)

  • Low-titer inhibitor: ≤5 BU

  • High-titer inhibitor: >5 BU

See Workup for more detail.

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