1. Plasma D-dimer assay is an assay to understand secondary fibrinolytic function.

Inspection principle: Anti-D-D monoclonal antibody is coated on latex particles. If there is D-dimer in receptor plasma, antigen-antibody reaction will occur, and latex particles will aggregate. However, this test can be positive for any bleeding with blood clot formation, so it has low specificity and high sensitivity.

2. There are two sources of D-dimer in vivo

(1) Hypercoagulable state and secondary hyperfibrinolysis;

(2) thrombolysis;

The D-dimer mainly reflects the fibrinolytic function. Increased or positive seen in secondary hyperfibrinolysis, such as hypercoagulable state, disseminated intravascular coagulation, renal disease, organ transplant rejection, thrombolytic therapy, etc.

3. As long as there is active thrombosis and fibrinolytic activity in the body's blood vessels, D-dimer will increase.

For example: myocardial infarction, cerebral infarction, pulmonary embolism, venous thrombosis, surgery, tumor, disseminated intravascular coagulation, infection and tissue necrosis can lead to increased D-dimer. Especially for the elderly and hospitalized patients, due to bacteremia and other diseases, it is easy to cause abnormal blood coagulation and lead to increased D-dimer.

4. The specificity reflected by D-dimer does not refer to the performance in a specific specific disease, but to the common pathological characteristics of this large group of diseases with coagulation and fibrinolysis.

Theoretically, the formation of cross-linked fibrin is thrombosis. However, there are many clinical diseases that may activate the coagulation system during the occurrence and development of the disease. When cross-linked fibrin is produced, the fibrinolytic system will be activated and the cross-linked fibrin will be hydrolyzed to prevent its massive "accumulation". (clinically significant thrombus), resulting in markedly elevated D-dimer. Therefore, elevated D-dimer is not necessarily a clinically significant thrombosis. For some diseases or individuals, it may be a pathological process.