The partial thromboplastin time (PTT) or activated partial thromboplastin time (aPTT or APTT) is a medical test that characterizes blood coagulation, also known as clotting.
This test is useful for monitoring heparin therapy (unfractionated heparin), screening for certain coagulation factor deficiencies and detection of coagulation inhibitors such as lupus anticoagulant.
The aPTT is considered a more sensitive version of the PTT and is used to monitor the patient’s response to heparin therapy. The reference range of the aPTT is 30-40 seconds. The reference range of the PTT is 60-70 seconds.
