D-dimer

D-dimer is a small protein fragment present in the blood after a blood clot is degraded by fibrinolysis. It is named so because it contains two D fragments of the fibrin protein joined by a cross-link.

Overview

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 patients 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.

Clinical Use

In patients suspected of disseminated intravascular coagulation (DIC), D-dimer is a useful test. If DIC is suspected, D-dimer levels will be very high. In patients with suspected pulmonary embolism (PE) or deep vein thrombosis (DVT), D-dimer testing has been shown to be sensitive but not specific. In other words, a negative D-dimer is useful for ruling out PE or DVT, but a positive D-dimer does not confirm either diagnosis.

Interpretation

D-dimer is elevated in any condition in which fibrin is formed and then broken down. Therefore, its concentration increases in conditions such as deep vein thrombosis, pulmonary embolism, myocardial infarction, and infection. However, it is also often elevated in pregnancy, surgery, trauma, and cancer, limiting its specificity.

See Also

• Deep vein thrombosis
• Pulmonary embolism
• Myocardial infarction
• Disseminated intravascular coagulation

References

D-dimer Resources
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