Partial Thromboplastin Time

Activated Partial Thromboplastin Time, APTT (Activated Parital Thromboplastin Time), PTT (Partial Thromboplastin Time)

What To Think About

• The partial thromboplastin time (PTT) and activated partial thromboplastin time (APTT) may be normal in people who have inherited bleeding disorders but have only mild symptoms.
• The APTT is used to check treatment of people who are using heparin or other blood-thinning medicine to prevent blood clots.
• Sometimes people who use heparin have a higher APTT because of other substances in their blood and not because of blood-thinning medicines. A test called the heparin neutralization assay may be done to see if this is true.
• Another blood clotting test, called prothrombin time (PT), measures other clotting factors. Partial thromboplastin time and prothrombin time are often done at the same time to check for bleeding problems. For more information, see the medical test Prothrombin Time.
• An PTT or APTT is done regularly in people who have bleeding or clotting problems. The tests are also done before procedures or surgeries where too much bleeding may be a concern.

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Author:	Robin Parks, MS	Last Updated: September 15, 2008
Medical Review:	Anne C. Poinier, MD - Internal Medicine Brian Leber, MDCM, FRCPC - Hematology
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