Coagulation laboratory tests
Factor VIII inhibitor assay / Bethesda assay

Author: Jeremy Parsons, M.D. (see Authors page)

Revised: 12 May 2016, last major update June 2012

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

PubMed Search: Factor VIII inhibitor assay / Bethesda assay

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