In vascular surgery, hematological examinations are mainly used to assess the patient’s blood physiological status, monitoring of various drug therapies and evaluation of their efficacy. In most peripheral vascular surgical diseases, in addition to vascular wall lesions, there are pathological changes such as abnormal platelet count and function, imbalance of dynamic balance between coagulation, anticoagulation and fibrinolytic systems, and abnormal changes in hemodynamics and blood rheology, which lead to bleeding or thrombosis. During the process from specimen collection to laboratory testing, unnecessary interfering factors should be minimized to improve the accuracy and reliability of the test results. I. Status of the subject Before blood collection, we should know whether the patient is pregnant, strenuously active, taking aspirin or contraceptive drugs, etc.; whether there is congenital or acquired coagulation factor deficiency; especially we should pay attention to the presence of liver diseases, or diseases causing impaired absorption or utilization of vitamin K and vitamin C, etc. All of these factors can affect the results of the hematology test. In addition, it is best to collect blood on an empty stomach. Collection and transfer of blood specimens The collection and transfer of blood specimens includes the following items. When collecting blood specimens, the syringe must be clean and dry, and it is best to collect blood in one successful puncture. A small amount of blood should be drawn by puncturing a syringe first, and then a different syringe should be used to take the blood sample in order to minimize the mixing of tissue fluid. The tissue fluid contains tissue thrombin, which activates the exogenous coagulation system and accelerates the coagulation process, thus affecting the test results. In addition, it can also lead to platelet aggregation due to thrombin formation. Take care not to froth or clot the blood sample during the blood collection process. The ratio of blood sample to anticoagulant should be accurate, usually 9:1. The tube should be clean and dry, and the syringe needle should be removed after blood collection and the blood sample injected slowly along the wall of the tube. The blood needs to be mixed well with the anticoagulant, but shaking should be avoided. For blood specimens used for platelet function tests, silicone-coated utensils are preferred. Other tests should be performed in appropriate tubes and sample doses according to specific requirements. General specimens should be sent immediately. If the specimen cannot be forwarded in time, it should be sent within the time required for each test. A dimer >0.5 mg/L as a criterion for the diagnosis of DIC (disseminated intravascular coagulation) has a positive rate of 96% and a specificity of 97%. When reflecting thrombin and fibrinolytic activity in vivo, D-dimer is the most desirable and has a higher diagnostic value than platelets, prothrombin time and fibrinogen content. Deep venous thrombosis (DVT) can be completely excluded when D-dimer <0.2 mg/L, but it cannot be used as a positive diagnostic indicator for DVT. （Plasma D-dimer levels are significantly elevated at the onset of (infarction) and can continue to rise 6 hours after infarction, reflecting thrombus formation in vivo. After thrombolytic therapy, the thrombus dissolves rapidly and the plasma D-dimer level rises sharply. The D-dimer level decreases rapidly if the thrombolytic drug has reached its efficacy, and if it remains at a high level after the increase, it indicates that the dosage of the thrombolytic drug is insufficient. the D-dimer rises to its peak at 6 hours after thrombolysis and decreases to the pre-thrombolytic level at 24 hours.