Coagulation laboratory tests

Prekallikrein assay

Topic Completed: 1 November 2012

Minor changes: 23 September 2020

Copyright: 2002-2022,, Inc.

PubMed Search: Prekallikrein assay [title]

Jeremy C. Parsons, M.D.
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Table of Contents
Definition / general
Cite this page: Parsons JC. Prekallikrein assay. website. Accessed January 17th, 2022.
Definition / general
  • Also known as Fletcher factor

  • Screening assays: preincubate PTT sample for 10 minutes prior to adding calcium; a prolonged PTT that shortens after the 10 minute preincubation is suspicious for prekallikrein deficiency

  • PTT performed with elagic acid as the intrinsic pathway activator will be normal in prekallikrein deficiency

  • Specific assay: preincubate patient plasma with prekallikrein-deficient plasma for 1 minute, then add calcium and perform PTT; prekallikrein level is determined from a standard curve of prekallikrein vs. PTT (Thromb Res 2002;105:463)

  • Interference is due to hirudin, argatroban, danaparoid and heparin (add heparinase)
  • Reference range is 60 - 140% of normal; newborn levels are lower, but increase to near adult levels by age 6 months

  • Indications: prolonged PTT corrected with mixing study, factors VIII, IX, XI and XII are normal, PT and fibrinogen are normal, lupus anticoagulant assays are negative
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