The partial thromboplastin time (PTT), also known as activated partial thromboplastin time (aPTT or APTT), is a laboratory test used to assess the efficiency of both the contact activation pathway and the common coagulation pathway in the blood clotting process. The aPTT is commonly employed as a starting point in the investigation of bleeding or thrombotic (blood clot) events. It is often part of pre-surgical screening to evaluate bleeding tendencies. Additionally, aPTT is used to monitor patients on heparin therapy to ensure adequate anticoagulation levels.
This test can also provide valuable insight into complications associated with conditions like disseminated intravascular coagulation (DIC) and may be prolonged in liver disease, as the liver produces most coagulation factors. In cases of thrombosis or recurrent miscarriages, the aPTT can be used in the evaluation for antiphospholipid syndrome.
When a patient is undergoing heparin therapy, aPTT levels are regularly monitored to ensure proper anticoagulation. In patients transitioning from heparin to warfarin therapy, both the aPTT and prothrombin time (PT) are monitored until the patient stabilizes on warfarin alone.
