Coagulation laboratory tests
Factor VIII inhibitor assay / Bethesda assay

Topic Completed: 1 June 2012

Revised: 7 January 2019, last major update June 2012

Copyright: (c) 2002-2016,, Inc.

PubMed Search: Factor VIII inhibitor assay / Bethesda assay

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Cite this page: Parsons J. Factor VIII inhibitor assay / Bethesda assay. website. Accessed June 7th, 2020.
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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