PTT (Partial Thromboplastin Time)

PTT detects nearly all abnormalities in clotting, due to deficiencies in clotting factors or circulating anticoagulants.

It is frequently used to monitor heparin therapy.

A modification of the test, "Activated PTT," or APTT, is basically the same as PTT, but is slightly more sensitive.

Prolonged PTT is associated with:

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

Therapeutic Range (Heparin Therapy)

  • 2-2.5 times the normal

Normal Values*

PTT 30-45 seconds 
APTT 16-25 seconds
Therapeutic Range on oral anticoagulants 2-2.5 times normal

*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.


Gynecology and Obstetrics CD-ROM
Volumes 1-6
2004 Edition
Lippincott Williams & Wilkins
Copyright 2004
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