Partial thromboplastin time (PTT)

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APTT; PTT; Activated partial thromboplastin time

The normal value will vary between laboratories. In general, clotting should occur between 25 to 35 seconds. If the person is taking blood thinners, clotting takes up to two and a half times longer.

Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

An abnormal (too long) PTT result may be due to:

• Disseminated intravascular coagulation (DIC)
• Factor XII or Factor XI deficiency
• Hemophilia A
• Hemophilia B
• Hypofibrinogenemia
• Liver disease
• Lupus anticoagulants
• Malabsorption
• Vitamin K deficiency
• Von Willebrand's disease

Review Date: 02/13/2011
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org).

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