PT: Prothrombin time is a screening test to check exogenous coagulation factors, which is used to confirm the existence of defects or inhibitors of congenital or acquired fibrinogen, prothrombin, coagulation factors V, VII and X, and also to monitor the dosage of oral anticoagulants. It is the first choice for monitoring oral anticoagulants.

TT Thrombin Time Measurement The prolongation of thrombin time can be seen in the increase of heparin or the existence of heparin-like anticoagulants, such as SLE, liver disease and nephropathy, and the increase of fibrinogen degradation products (FDP), such as DIC and primary fibrinolysis.

APTT is a screening test to check endogenous coagulation factors, which is used to confirm the defects of congenital or acquired coagulation factors Ⅷ, Ⅷ and whether there are corresponding inhibitors. At the same time, APTT can also be used to check whether coagulation factors, kallikrein and high molecular weight kallikrein are lacking. APTT has become the first choice to monitor unfractionated heparin because of its high sensitivity and the action pathway of heparin is mainly endogenous coagulation pathway.

Fibrinogen fibrinogen, or coagulation factor I, is the main protein in the process of coagulation. Except for physiological stress and late pregnancy, the increase of FIB mainly occurs in acute infection, burn, atherosclerosis, acute myocardial infarction, autoimmune diseases, multiple myeloma, diabetes, pregnancy-induced hypertension, acute nephritis and uremia, while the decrease of FIB mainly occurs in DIC, primary hyperlysis, severe hepatitis, sclerotherapy and thrombolytic therapy. Simultaneous detection of prothrombin time, activated partial thromboplastin time and fibrinogen has been used to screen whether the coagulation mechanism of patients is normal in clinic, especially in cardiothoracic surgery, orthopedics and obstetrics and gynecology.