Activated Partial Thromboplastin Time (aPTT/PTT) measures how long it takes blood to clot through the intrinsic pathway. It is used to evaluate clotting disorders and monitor heparin therapy.
Category: Coagulation
Also known as: ptt, aptt, partial thromboplastin time, activated partial thromboplastin time
Reference range: 25–35 seconds (Source: ABIM)
Standard unit: seconds
High values may indicate
Prolonged aPTT may indicate clotting factor deficiencies (such as hemophilia), heparin therapy, von Willebrand disease, lupus anticoagulant, or liver disease.
Low values may indicate
Shortened aPTT is uncommon but may indicate a hypercoagulable state or elevated factor VIII levels related to acute inflammation.