Coagulation
Coagulation laboratory tests
Prekallikrein assay
Author: Jeremy C. Parsons, M.D.
Last author update: 1 November 2012
Last staff update: 23 September 2020
Copyright: 2002-2023, PathologyOutlines.com, Inc.
PubMed Search: Prekallikrein assay [title]
Table of Contents
Definition / generalCite this page: Parsons JC. Prekallikrein assay. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/coagulationprekallekreinassay.html. Accessed June 3rd, 2023.
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
