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), 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 non-prescription 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 blood sample taken from a vein.
Partial thromboplastin time (PTT) is a blood test that measures the time it takes your blood to clot. Normal values may vary from lab to 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.
Reasons you may not be able to have the test or why the results may not be helpful include:
Other Works Consulted
- Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.
- Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
- Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.
|Primary Medical Reviewer||E. Gregory Thompson, MD - Internal Medicine|
|Primary Medical Reviewer||Donald Sproule, MD, CM, CCFP, FCFP - Family Medicine|
|Specialist Medical Reviewer||Joseph O'Donnell, MD - Hematology, Oncology|
|Last Revised||October 19, 2010|
Last Revised: April 19, 2012
This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information.