1.Definition
D-dimer is a specific degradation product resulting from cross-linking of fibrin monomers by activating factor XIII and then hydrolysis by fibrinolytic enzymes, and is a specific marker of the fibrinolytic process. d-dimer is derived from cross-linked fibrin clots lysed by fibrinolytic enzymes.
2.Normal range
Qualitative Negative.
Quantification Less than 200μg/L.
3.Check introduction
Plasma D-dimer assay is a test to understand the function of secondary fibrinolysis. There are many factors affecting this test, and the results must be verified when judging.
4.Clinical significance
D-dimer mainly reflects the fibrinolytic function.
An increased or positive level is seen in secondary fibrinolytic function, such as hypercoagulable state, diffuse intravascular coagulation, renal disease, organ transplant rejection, thrombolytic therapy, etc.
D-dimer is elevated whenever there is activated thrombus formation and fibrinolytic activity in the body’s blood vessels. Myocardial infarction, cerebral infarction, pulmonary embolism, venous thrombosis, surgery, tumors, diffuse intravascular coagulation, infection and tissue necrosis can all lead to elevated D-dimer. Especially for elderly people and hospitalized patients, diseases such as bacteraemia are likely to cause abnormal coagulation and lead to elevated D-dimer.
5.Physiological background
The fibrinolysis system is the most important anticoagulant system in the body and consists of four major components: plasmingen, plasmingen activator (e.g., t-PA, u-PA), plasmin, and plasmin inhibitor. plasmin activator inhibitor, PAI-1, antiplasmin). When fibrin clot is formed, in the presence of tPA, fibrinogen activation is converted into fibrin lysis, and fibrinolysis process starts, and fibrin lysis degrades fibrin clot to form various soluble fragments to form fibrin product (FDP), which is composed of the following substances: X-oligomer, D-dimer, and interstitial fragment (Intra). Dimer, Intermediate fragments, and Fragment E. Among them, X-oligomer and D-oligomer both contain D-dimer units.
The human fibrinolytic system, which plays an important role in maintaining the normal permeability of the blood vessel wall, maintaining the flow state of blood and tissue repair. increased levels of D-dimer in plasma indicate the presence of secondary fibrinolytic processes, and Mr. thrombin, followed by activation of the fibrinolytic system; and also reflects the local fibrinolytic activity or concentration in thrombosis exceeds plasma 2‰-antifibrinolytic activity or concentration. Thrombolytic therapy involves the use of drugs to activate the fibrinolytic system. FDP or D-dimer production is indicative of a thrombolytic effect.
Among the fibrin degradation products, only D-dimer cross-linked fragments can reflect the thrombolytic activity after thrombus formation. Therefore, theoretically, the quantitative assay of D-dimer can quantitatively reflect the thrombolytic effect of drugs and can be used to diagnose and screen newly formed thrombi. However, so far, the commercial D-dimer assays have some limitations. Among them, the colloidal gold immunofiltration assay for D-dimer is more often used by clinicians because of its rapid determination, high sensitivity, high negative predictive value and good reproducibility.
6.D-dimer determination clinical significance and clinical application
The determination of the main factors of fibrinolytic system is important for the diagnosis and treatment of fibrinolytic system diseases (such as DIC, various thrombosis) and diseases related to fibrinolytic system (such as tumor, pregnancy syndrome), as well as the monitoring of thrombolytic therapy.
Elevated levels of fibrin degradation product D indicate the presence of frequent fibrin degradation processes in the body. Therefore, fibrin D-dimer is a key indicator of deep vein thrombosis (DVT), pulmonary embolism (PE), and diffuse intravascular coagulation (DIC).
Clinical applications.
Deep vein thrombosis (DVT) diagnosis.
Comparative studies have shown that NycoCard D-Dimer and ELISA D-Dimer are nearly 100% consistent and sensitive in the negative diagnosis of DVT compared to venography. In contrast, the sensitivity of latex method was only 73%, and the consistency of results was 78%.
NycoCard D-Dimer is an important tool for early diagnosis and positive exclusion of DVT. It is convenient, rapid and cost-saving.
(1) Diagnosis of pulmonary embolism (PE) and arterial thrombosis.
(2) Diagnosis of diffuse intravascular coagulation (DIC).
(3) early testing of fibrinolytic mechanisms of action – pre-thrombotic risk evaluation.
(4) High risk of pregnancy and pre-eclampsia.
(5) monitoring of thrombosis process and thrombolytic therapy.
(6) Adjuvant diagnosis of tumors.