aPTT factor substitution 1 hour post incubation

A partial thromboplastin time (PTT) test uses a blood sample to measure the number of seconds it takes for your blood to 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, and your liver makes most of them.

A PTT test is used to check for problems with a specific group of blood clotting factors.