D-dimer Quick Facts
Molecular mass
- 195 000 D D-Dimer
- 247 000 D D-Dimer-E-Fragment
Biochemistry of D-dimer
D-dimer (D dimer, DDimer) is a specific fibrin degradation product (or FDP), a small protein fragment present in the blood, generated after a blood clot is degraded by fibrinolysis. It is so named because it contains two crosslinked D fragments of the fibrin protein. D-dimer is also known as “cross-linked fibrin degradation products”.
Cross-linking of soluble fibrin to the insoluble fibrin is the last step in plasmatic coagulation. Fibrinolysis as the counter reaction has the task of lysing the fibrin clot. Plasmin is the central enzyme in this process and cleaves the fibrin clot at specific sites. This process takes place in several steps via high molecular fragments and soluble aggregates down to the D-dimer and D-dimer-E fragments, which cannot be any further degraded by plasmin. The determination of D-dimer allows a direct determination of plasmin activity.
Clinical or Research use of D-dimer
D-dimer concentration may be determined by a blood test to help diagnose thrombosis. Since its introduction in the 1990s, it has become an important test performed in subjects with suspected thrombotic disorders. While a negative result practically rules out thrombosis, a positive result can indicate thrombosis but does not rule out other potential causes. Its main use, therefore, is to exclude thromboembolic disease where the probability is low. In addition, it is used in the qualification of the blood disorder disseminated intravascular coagulation (DIC).
Elevated DDimer levels are found in cases of DIC, deep vein thrombosis (DVT) and pulmonary embolism (PE) but other circumstances may also lead to high D-Dimer levels such as old age, pregnancy, cancer, liver disease and infection.
Elevated concentrations of D-dimer can be observed in a variety of diseases and during fibrinolytic therapy (e.g. with streptokinase and t-PA). In all diseases with an elevated activation (e.g. thromboembolism and DIC) hyperfibrinolysis has been observed as the counter reaction to the elevated fibrin formation. D-dimer is a marker for this hyperfibrinolysis. Elevated D-dimer concentrations thus can be observed in thromboembolic diseases (pulmonary embolism, deep venous thrombosis), leukaemia and sepsis, intra- and postoperative, in physical and mental stress and during extra corporeal circulation.
D-Dimer ELISA
The ELISA system has a higher sensitivity when compared with latex agglutination tests thus giving an improved aid in the qualification for the exclusion of venous thromboembolism (VTE).
Clinical or Research use of D-dimer
- Monitoring of hyperfibrinolysis in DIC
- Suspected hyperfibrinolysis as the cause of a hemorrhagic diathesis
- Complications in pregnancy: diagnosis of a severe preeclampsia
- Exclusion diagnosis in suspected venous thrombosis and pulmonary embolism with negative test results and/or a stronger suspicion with positive results.