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Partial thromboplastin time (PTT) is a blood test that measures the time it takes your blood to clot. A PTT test can be used to check for bleeding problems.
Blood clotting factors are needed for blood to clot (coagulation). The partial thromboplastin time is an important test because the time it takes your blood to clot may be affected by:
Another blood clotting test, called prothrombin time (PT) or INR (international normalized ratio), measures other clotting factors. Partial thromboplastin time and prothrombin time are often done at the same time to check for bleeding problems caused by a problem with the clotting factors.
Partial thromboplastin time (PTT) is done to:
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.
Many medicines can change the results of this test. Be sure to tell your doctor about all the nonprescription and prescription medicines you take.
The health professional drawing blood will:
The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.
There is very little chance of a problem from having a blood sample taken from a vein.
Partial thromboplastin time (PTT) is a blood test that measures the time it takes your blood to clot.
The normal values listed here-called a reference range-are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
Partial thromboplastin time (PTT):
Activated partial thromboplastin time (APTT):
The heparin dose is changed so that the PTT or APTT result is about 1.5 to 2.5 times the normal value.footnote 1
Reasons you may not be able to have the test or why the results may not be helpful include:
Pagana KD, Pagana TJ (2014). Mosby's Manual of Diagnostic and Laboratory Tests, 5th ed. St. Louis: Mosby.
Other Works Consulted
Chernecky CC, Berger BJ (2013). Laboratory Tests and Diagnostic Procedures, 6th ed. St. Louis: Saunders. Fischbach F, Dunning MB III (2015). A Manual of Laboratory and Diagnostic Tests, 9th ed. Philadelphia: Wolters Kluwer Health. Pagana KD, Pagana TJ (2014). Mosby's Manual of Diagnostic and Laboratory Tests, 5th ed. St. Louis: Mosby.
ByHealthwise Staff Primary Medical Reviewer E. Gregory Thompson, MD - Internal Medicine Adam Husney, MD - Family Medicine Martin J. Gabica, MD - Family Medicine
Current as ofDecember 6, 2017
Current as of:
December 6, 2017
E. Gregory Thompson, MD - Internal Medicine & Adam Husney, MD - Family Medicine & Martin J. Gabica, MD - Family Medicine
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Children's Hospital's main campus is located in the Lawrenceville neighborhood. Our main hospital address is:
UPMC Children’s Hospital of Pittsburgh
One Children’s Hospital Way
4401 Penn Ave.
Pittsburgh, PA 15224
In addition to the main hospital, Children's has many convenient locations in other neighborhoods throughout the greater Pittsburgh region.
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