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PT (Prothrombin Time)

Prothrombin is a protein produced in the liver. It plays an important role in blood clotting: Reductions in prothrombin will lead to decreased clotting ability of the blood.

The PT (ProTime, Prothrombin Time) measures impairment of the clotting effects of prothrombin, fibrinogen, and coagulation Factors II, VII, IX, and X.

Any process that interferes with the production of prothrombin (liver disease, Vitamin K deficiency, Coumarin-based anticoagulants) may impair the ability of blood to clot, and can be measured by a prolongation of the Prothrombin Time (PT).

Patients being treated with oral anticoagulants are monitored with PT, to make sure they are within the therapeutic range.

If they aren't receiving enough anticoagulant, the treatment may be ineffective
If they receive too much anticoagulant, they may lose too much ability to clot and sustain injury as a consequence.

Prolonged PT is associated with:

Liver disease
Vitamin K deficiency
Anticoagulant (Coumarin, Coumadin) therapy
DIC

Therapeutic Range

2-2.5 times the normal
Not more than 30 seconds

Normal Values*

Men-Women	10-14 seconds (100%)
Therapeutic Range on oral anticoagulants	2-2.5 times normal, but not >30 seconds

*These are general values taken from a variety of sources. The actual normal values may vary from lab to lab and from one type of testing protocol to another.

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Bureau of Medicine and Surgery
Department of the Navy
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Operational Medicine
Health Care in Military Settings
CAPT Michael John Hughey, MC, USNR
NAVMED P-5139
January 1, 2001

United States Special Operations Command
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*This web version is provided by The Brookside Associates Medical Education Division. It contains original contents from the official US Navy NAVMED P-5139, but has been reformatted for web access and includes advertising and links that were not present in the original version. This web version has not been approved by the Department of the Navy or the Department of Defense. The presence of any advertising on these pages does not constitute an endorsement of that product or service by either the US Department of Defense or the Brookside Associates. The Brookside Associates is a private organization, not affiliated with the United States Department of Defense.

Operational Medicine 2001
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