partialThromboplastinTimePTTTest
Reviewed
Also called: activated partial thromboplastin time, aPTT, intrinsic pathway coagulation factor profile
A PTT test measures the number of seconds it takes for your blood to clot. It helps check how many of a specific group of clotting factors you have and how well they are working. The test is used to find the cause of too much bruising or bleeding, monitor people taking heparin, check for clotting problems related to autoimmune diseases such as lupus and antiphospholipid syndrome, and assess bleeding risk before surgery if you have a history of excessive bleeding.
Specimen: blood sample from a vein in your arm
Why this test may be ordered
- Problems with bleeding or bruising and the cause is not known
- A blood clot in a vein or artery
- Liver disease
- A history of several miscarriages
- A bleeding or clotting disorder and you don’t know which clotting factors are involved
Preparation and collection
You don't need any special preparations for a PTT test.
A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. This usually takes less than five minutes.
There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
Understanding results
Your PTT test results will show how much time it took for your blood to clot. Results are usually given as a number of seconds. In general, if your blood took longer than normal to clot on a PTT test, it may be a sign of certain conditions. If your blood clotted faster than normal, it may be a sign of other conditions. Even if your sample clotted faster or slower than usual, that doesn’t necessarily mean you have a medical condition. Talk with your provider to learn what your test results mean for you.
- Blood took longer than normal to clot: May be a sign of hemophilia A or B, liver disease, a lack of vitamin K, certain genetic disorders (such as Von Willebrand disease), too much heparin, certain types of leukemia, or autoimmune diseases (such as lupus anticoagulant syndrome). Autoimmune diseases can affect your PTT test results by showing a slower clotting time than you actually have. Limitation: There can be a difference between how fast your blood clots in a test setting and how fast it clots in your body. If your provider thinks that an autoimmune disease is causing a clotting problem, they will usually order more tests to make a diagnosis. Next step: Prompt
- Blood clotted faster than normal: May be a sign of the early stage of disseminated intravascular coagulation (DIC), high levels of clotting factors (such as during inflammation, pregnancy, or cancer), or advanced cancer of the ovaries, colon, or pancreas. Limitation: There can be a difference between how fast your blood clots in a test setting and how fast it clots in your body. Even if your sample clotted faster than usual, that doesn’t necessarily mean you have a medical condition. Next step: Prompt
- There can be a difference between how fast your blood clots in a test setting and how fast it clots in your body.
- Autoimmune diseases can affect your PTT test results by showing a slower clotting time than you actually have.
- Even if your sample clotted faster or slower than usual, that doesn’t necessarily mean you have a medical condition.
What to do next
Talk with your provider to learn what your test results mean for you. If your results are unusual, your provider may order more tests.
- What do my PTT test results mean for me?
- Do I need any follow-up tests based on my results?
- Should I be concerned about bleeding or clotting risks?
Evidence source
U.S. National Library of Medicine: partialThromboplastinTimePTTTest