APTT is an abbreviation for activated partial thromboplastin time, which is the time required to observe plasma clotting by adding activated partial thromboplastin time reagents to the plasma under test.APTT is the more sensitive and most commonly used screening test to determine the endogenous coagulation system, with a normal range of 31-43 seconds and a clinical significance of more than 10 seconds above the normal control. In clinical practice, prolonged APTT is common in various coagulation factor deficiency diseases, while patients often have a tendency to bleed and symptoms, common diseases are vitamin K deficiency, fibrinogen deficiency, and patients with disseminated intravascular coagulation and heparin application. shortened APTT indicates that the blood is in a hypercoagulable state, common in thrombotic diseases, such as cerebral thrombosis, coronary artery disease, etc.