Normal 30-40 seconds Indications Identifying congenital deficiencies in clotting Monitoring heparin therapeutic levels (PT for warfarin) Monitoring effects of: Liver Disease Protein Deficiency Fat malabsorption on clotting Description Activated Partial Thromboplastin Time (aPTT) is a test that measures the amount of time it takes for a fibrin clot to form after reagents have been added to the specimen. It is useful in diagnosing clotting disorders. In conjunction with PT it can be used to differentiate the specific factor that may be missing. What would cause increased (Prolonged) levels? Vitamin K Deficiency Disseminated Intravascular Coagulation (DIC) Hemodialysis Patients Afibrinogenemia Polycythemia Liver disease Von Willebrand Disease. What would cause decreased levels? N/A