Coagulation laboratory tests
Factor VIII assay

Topic Completed: 1 June 2012

Revised: 7 January 2019, last major update June 2012

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

PubMed Search: Factor VIII assay [title]

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Cite this page: Parsons J. Factor VIII assay. website. Accessed June 7th, 2020.
Definition / general
  • Assay is usually a PTT - based clotting assay that measures factor VIII activity
  • Use severely deficient factor VIII plasma as substrate for one stage clotting assay, although there is tremendous interlaboratory variability
  • Can also use chromogenic assay, particularly when assessing B - chain deleted recombinant Factor VIII (i.e. “Refacto”)

  • Low levels:
    • Hemophilia, vWF disease with decreased vWF antigen levels, delay in transporting specimen to lab

  • Note:
    • Levels are not greatly decreased at birth or throughout childhood
    • Levels may increase during pregnancy

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