Partial thromboplastin time

The partial thromboplastin time (PTT) or activated partial thromboplastin time (aPTT or APTT) is a medical test that characterizes blood coagulation. A historic name for this measure is the Kaolin cephalin clotting time (KccT). Apart from detecting abnormalities in blood clotting, partial thromboplastin time is also used to monitor the treatment effects with heparin, a widely prescribed drug that reduces blood's tendency to clot. Partial thromboplastin time (PTT) measures the overall speed at which blood clots by means of two consecutive series of biochemical reactions known as the "intrinsic" (now referred to as the contact activation pathway) and common coagulation pathways. The partial thromboplastin time (PTT) is used in conjunction with another measure of how quickly blood clotting takes place called the prothrombin time (PT). The prothrombin time measures the speed of clotting by means of the extrinsic pathway (also known as the tissue factor pathway).