Coagulation
Coagulation laboratory tests
Factor assays

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

Revised: 11 May 2016, last major update June 2012

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

PubMed Search: Factor assays [title]

Cite this page: Factor assays. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/coagulationfactorassays.html. Accessed December 9th, 2016.
Definition / General
  • PT (factors II, V, VII, X) or PTT (factors V, VIII, IX, XI, XII) based reactions, performed by mixing patient plasma with plasma that is deficient in the factor being measured
  • The rate limiting reactant is the deficient factor which must be supplied by the patient
  • PT or PTT is compared to standard curve, to determine amount of factor present in patients plasma
  • Used to determine the etiology of a prolonged PT or PTT
  • Factor levels are expressed as % of normal plasma concentration, or units per mL of normal plasma
  • Reference range is often 60-140% (should be determined based on the laboratorys patient population)
  • Perform at multiple dilutions to rule out an inhibitor - at higher dilutions, inhibitor interference should decrease due to dilution of the inhibitor (this gives a nonlinear curve)
  • Can also use chromogenic assays to quantitate
  • Levels at birth of factors other than factor VIII are 10 - 100% of adult levels, but reach adult levels at 6 months
Additional References