Activated partial thromboplastin time

The partial thromboplastin time or activated partial thromboplastin time is a blood test that characterizes the coagulation of the blood. A historical name for this measure is the kaolin-cephalin clotting time, reflecting kaolin and cephalin as materials historically used in the test.

The partial thromboplastin time (PTT) or activated partial thromboplastin time (aPTT or APTT) is a performance indicator measuring the efficacy of both the “intrinsic” (now referred to as the contact activation pathway) and the common coagulation pathways. Apart from detecting abnormalities in blood clotting, it is also used to monitor the treatment effects with heparin, a major anticoagulant. It is used in conjunction with the prothrombin time (PT) which measures the extrinsic pathway. Kaolin cephalin clotting time (KccT) is a historic name for the activated partial thromboplastin time.

Normal values < 36 secs.