Activated partial thromboplastin time is a screening test to check endogenous coagulation factors. Shortened activated partial thromboplastin time is seen in: 1, increased activity of coagulation factors VIII and X; 2, thrombocytosis; 3, hypercoagulable state: such as procoagulant substances into the blood and increased activity of coagulation factors and other conditions, DIC hypercoagulable phase, unstable angina, cerebrovascular lesions, diabetic vascular lesions, cerebral infarction; 4, hyperemesis and nephritis syndrome, unsuccessful venipuncture mixed with tissue fluid; 5, pre-thrombotic state and thrombotic diseases: such as myocardial infarction, pulmonary infarction, deep vein thrombosis, etc.