Partial Thromboplastin Time
Alternate Names : PTT, Activated Partial Thromboplastin Time, APTT
The partial thromboplastin time (PTT) test helps measure the ability of the blood to clot normally. It is very similar to the prothrombin time (PT) test. These two tests are often ordered together.
At least 12 different proteins are involved in clotting. The PTT and PT test each measure the function of some of these proteins.
Who is a candidate for the test?
This test may be done:
when a person has a bleeding problem
to monitor a person who is taking blood-thinning medicine
before surgery to make sure a person will not bleed too much during the operation
How is the test performed?
A blood sample is usually taken from a vein on the forearm or hand. The skin over the vein is first cleaned with an antiseptic. Next, a strong rubber tube, or tourniquet, is wrapped around the upper arm. This restricts blood flow through the veins in the lower arm and causes them to enlarge.
A small needle is gently inserted into a vein and the tourniquet is removed. Blood flows from the vein through the needle. It is collected in a syringe or vial. After the needle is withdrawn, the puncture site is covered to prevent bleeding. The blood sample is sent to a lab for testing.