Coagulation laboratory tests
Prekallikrein assay

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

Revised: 17 May 2016, last major update November 2012

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

PubMed Search: Prekallikrein assay [title]

Table of Contents
Definition / general
Cite this page: Prekallikrein assay. website. Accessed May 22nd, 2018.
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