D- dimers are proteins which occur as degradation products of fibrin in the blood during fibrinolysis. D- dimers are a biomarker for the dissolution of blood clots and their concentration in the blood is therefore determined for the diagnosis of thrombosis. A negative value can exclude thrombosis, while a positive value can have different causes. The name is derived from the dimer structure of the D- fragments.
The cross-linked via the D- domains of fibrin is cleaved by the endopeptidase plasmin, the smallest one of the resulting fragments are referred to as dimers.
The D -dimer level is determined by highly specific antibodies to the cross-linking region in an immunoassay. The agglutination can be photometrically measured as turbidity. The normal range is strongly method-dependent. The increase in D- dimer in the plasma is due to the coagulation and subsequent clot dissolution. Values in the respective specified by the laboratory reference range (eg, below 0.5 mg / liter; plasma ) are used for exclusion diagnosis of pulmonary embolism, DIC ( Disseminated intravascular coagulation ) or deep vein thrombosis. In addition, the laboratory value of D-dimer can be used for monitoring the course of thrombolytic therapy.
The D- dimer can also be malignant ( malignant ) tumor diseases, after surgery in the context of wound healing, liver cirrhosis, leukemia, in other serious diseases, or increased in pregnancy. It is a sensitive but relatively non-specific diagnostic parameters. Especially in the case of pulmonary embolism and deep 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 excluded with high probability. The sensitivity is> 95 %, the specificity < 50%, the negative predictive value was 95%. To complete the statement of the Wells score or the Geneva score can be used.