During the formation of clots, fibrin is produced in excess and mechanisms will destroy it. Among the degradation products of fibrin, one can find D-dimers, which, when they are increased, let suspect the presence of a phlebitis or a pulmonary embolism.
Definition: what are D-dimers?
THE D-dimers are molecules resulting from fibrin destruction, a protein produced primarily during blood clotting. The presence of D-dimers in the blood is normal, but at a low rate, and its dosage allows, in the event of a significant increase, to detect the presence of a blood clot or thrombus. The D-Dimers are dosed if deep vein thrombosis (phlebitis) or pulmonary embolism is suspected. However, D-Dimers are not specific, and are increased in many other cases (elderly, certain infections, pregnant women).
What is the normal D-dimer level?
The level of D-dimer in the blood is normally lower than 500 micrograms per literbut like any blood test, standards may vary slightly from lab to lab.
D-Dimers are measured in case of suspected deep vein thrombosis (phlebitis) or pulmonary embolism.
The blood test for D-dimers Made by a simple blood test. It allows to strongly suspect diagnosis of pulmonary embolism and deep vein thrombosis when increased. Pulmonary embolism is an occlusion of the pulmonary artery by a clot. She is one of the most common and serious complications of phlebitis. In nearly 3 out of 4 cases, pulmonary embolism, which is an emergency, is caused by a blood clot that initially formed in a vein in the legs. The blood assay of D-dimers is interesting to perform when the diagnosis of deep vein thrombosis or pulmonary embolism is evoked. It allows to confirm the diagnosis of thrombosis or pulmonary embolism, but also in many situations, to avoid performing certain invasive examinations unnecessarily. This test can be performed on an emergency basis.
What does low D-dimer mean?
This test is more than 95% sensitive. A low rate of D-dimers practically 100% exclude pulmonary embolism or deep vein thrombosis. A negative test lower than 500 micrograms per liter makes it possible to formally eliminate a pulmonary embolism and/or phlebitis. At any rate, its negative predictive value is excellent : the absence of an increase in the blood level of D-dimers rules out the diagnosis of pulmonary embolism or deep vein thrombosis.
What does high D-dimer mean?
However, even if this test is very sensitive, it is not very specific: the D-dimers can also be increased during certain situations and cause “false positives”: the formation of small quantities of fibrin can take place in the course of sometimes physiological situations such as during pregnancy, inflammatory pathologies, cancers, hematoma resorption or after surgery. Thus, an elevation of D-dimers does not necessarily mean the presence of a pulmonary embolism or a deep vein thrombosis. An increase in D dimers therefore does not allow an immediate diagnosis of the presence of thrombosis. He is essential to carry out other examinations to affirm the presence of a clot such as an echo-doppler looking for signs of phlebitis of the lower limbs or an angio-scan when suspected pulmonary embolism.
When to consult?
When a D-dimer result is high, it is necessary to see a doctor who will be able to tell the difference between a “false positive” and the presence of thrombosis. In the slightest doubt, he will urgently prescribe the essential additional examinations. Conversely, facing unusual shortness of breath, chest pain, or signs of phlebitis, it is necessary to consult so that the doctor prescribes a dosage of D-dimers. At the slightest doubt about phlebitis, a simple dosage of D-dimers is quick and allows a quick diagnosis. It is nevertheless important toInterpret the results according to the age because they increase physiologically with this one.