Coagulation laboratory tests

Factor VIII inhibitor assay / Bethesda assay

Topic Completed: 1 June 2012

Minor changes: 18 September 2020

Copyright: 2002-2021,, Inc.

PubMed Search: Factor VIII inhibitor assay / Bethesda assay

Jeremy C. Parsons, M.D.
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Cite this page: Parsons JC. Factor VIII inhibitor assay / Bethesda assay. website. Accessed October 25th, 2021.
Definition / general
  • Methodology:
    • Prepare serial dilutions of patient plasma in citrated saline from 1 : 1 to 1 : 160 (or higher)
    • Mix each dilution with an equal volume of normal plasma containing a normal amount of coagulation factors, incubate for 2 hours, then perform factor VIII assay
    • Titer of inhibitor is dilution that inhibits 50% of factor VIII in assay
    • Can use porcine Factor VIII to assess cross-reactivity and assist in therapeutic decisions
Additional references
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