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Coagulation laboratory tests

Prekallikrein assay

Reviewer: Jeremy Parsons, M.D. (see Reviewers page)
Revised: 10 Feburary 2013, last major update November 2012
Copyright: (c) 2002-2013, PathologyOutlines.com, Inc.


● Prekallikrein is 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

End of Coagulation > Coagulation laboratory tests > Prekallikrein assay

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