Partial Thromboplastin Time

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

Why It Is Done

Partial thromboplastin time (PTT) is done to:

• Find a cause of abnormal bleeding or bruising.
• Check for low levels of blood clotting factors. The lack of some clotting factors can cause bleeding disorders such as hemophilia.
• Check for conditions that cause clotting problems. Conditions such as antiphospholipid antibody syndrome or lupus anticoagulant syndrome develop when the immune system makes antibodies that attack blood clotting factors. This can cause the blood to clot easily in veins and arteries.
• Check blood clotting time before a surgery.
• Check to see if the dose of anti-clotting medicine is right.

The activated partial thromboplastin time (APTT) test is used after you take blood-thinners to see if the right dose of medicine is being used. If the test is done for this purpose, an APTT may be done every few hours. When the correct dose of medicine is found, you will not need so many tests.

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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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