. The aPTT is a test that measures the time it takes for blood to form a clot in the body. Normally, when a blood vessel is damaged, clotting factors will combine in a certain order to form a clot and quickly stop bleeding.
. This test helps evaluate the blood clotting process and is often used with other tests. It helps screen for deficiencie of clotting factors belonging to the intrinsic pathway, mainly factor VIII or the common coagulation pathway (II, V and X ...). Additionally, it is used to monitor unfractionated heparin therapy.