D-dimer

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D-dimer formation

D- dimers are proteins that occur as breakdown products of cross-linked fibrin in the blood during the body's own dissolution of a blood clot and are created by the reactive action of plasmin . They are a biomarker for the dissolution of blood clots called fibrinolysis , so their concentration in the blood is used to diagnose thrombosis . A negative value can rule out a thrombosis, while a positive value can have various causes. The name is derived from the dimer structure of the D fragments.

properties

The fibrin cross-linked via the D domains is cleaved by the endopeptidase plasmin; the smallest of the fragments formed are referred to as D dimers.

The D-dimer level is determined using highly specific antibodies against the crosslinking region in an immunoassay . The agglutination can be measured photometrically as turbidity. The normal range is heavily dependent on the method. The increase in D-dimer in plasma is a result of blood clotting and the subsequent fibrinolysis (clot dissolution). Values ​​in the respective reference range specified by the laboratory (e.g. below 500  µg / liter; plasma ) serve to exclude the diagnosis of pulmonary embolism , DIC ( disseminated intravascular coagulopathy ) or deep vein thrombosis . In addition, the laboratory value of the D-dimers can be used to monitor the progress of thrombolytic therapy.

The D-dimer can also be malignant (malignant) tumor disease control, after operations in the course of wound healing, liver cirrhosis , leukemia be increased if more serious illness or during pregnancy. It is a sensitive but relatively unspecific diagnostic parameter. Especially in pulmonary embolism and leg vein thrombosis (DVT), the D-dimers have a very high negative predictive value: If the concentration is not increased, pulmonary embolism or DVT can be ruled out with a high degree of probability. The sensitivity is> 95%, the specificity <50%, the negative predictive value is 95%. The Wells score or the Geneva score can be used to supplement the statement .

Web links

  • www.med4you.at : Determination of the D-dimer to diagnose or exclude deep vein thrombosis and pulmonary embolism; Univ.-Doz. Dr. med. Wolfgang Hübl

Individual evidence

  1. ↑ Jürgen Hallbach: Clinical chemistry for entry . Georg Thieme Verlag, April 2006, ISBN 978-3-13-106342-7 , p. 471– (accessed on July 26, 2012).