aPTT

Activated partial thromboplastin time (aPTT or PTT)

Activated Partial Thromboplastin Time (aPTT) test measures the time it takes for blood to clot, specifically evaluating the intrinsic and common coagulation pathways. It assesses the function of clotting factors such as factor VIII, IX, XI, and XII. aPTT is commonly used to monitor patients on heparin therapy and to diagnose clotting disorders like hemophilia or lupus anticoagulant syndrome. Prolonged aPTT indicates deficiencies in clotting factors or the presence of inhibitors (e.g., an excess of heparin), whereas shortened aPTT suggests hypercoagulability.