Partial Thromboplastin Time (PTT) Test

A partial thromboplastin time (PTT) test uses a blood sample to measure how long it takes for your blood to make a clot. Normally, when you get a cut or injury that causes bleeding, many different types of proteins in your blood work together to make a clot to stop the bleeding. These proteins are called coagulation factors or clotting factors.

If any of your clotting factors are missing, at a low level, or not working properly, your blood may: Clot too slowly after an injury or surgery. If this happens, you have a bleeding disorder. Bleeding disorders can cause serious blood loss.

Hemophilia is one type of bleeding disorder.; Clot too much and/or too quickly, even without an injury. This condition may lead to clots that block your blood flow and cause serious conditions, such as heart attack, stroke, or clots in the lungs.; A PTT test helps check a specific group of clotting factors. It helps show how much of these clotting factors you have and how well they're working.

A PTT test is often done with other tests that check clotting factors and how well they all work together.

Why this test is done

You may need a PTT test if you:

• Have problems with bleeding or bruising and the cause is not known
• Have a blood clot in a vein or artery
• Have liver disease (your liver makes most of your clotting factors).
• Have had several miscarriages
• Have been diagnosed with a bleeding or clotting disorder and don't know which clotting factors are involved
• Are taking heparin (to check how this medicine is affecting you, your health care provider may use a PTT test or another test instead).

How to prepare

You don't need any special preparations for a PTT test.

Sample type

Blood

Other names for this test

activated partial thromboplastin time, aPTT, intrinsic pathway coagulation factor profile