Thrombin converts fibrinogen to soluble fibrin by cleaving the fibrinopeptides A and B. The fibrin monomers polymerize spontaneously. Active factor XIII links two D‑domains and generates a solid fibrin clot. A new plasmin‑resistant antigenic determinant (“D‑Dimer”) is produced. Fragments containing D‑Dimer are accordingly formed during the degradation of a fibrin clot by plasmin. A large proportion of the fibrin degradation products consist of high molecular weight X‑oligomers. The D‑Dimer assay has a strong affinity for these high molecular weight degradation products. Only in vitro or during lysis therapy complete degradation to D‑Dimer molecules takes place. D‑Dimer is a very sensitive marker for the activation of coagulation.
In disseminated intravasal coagulation (DIC)/consumptive coagulopathy, fibrin degradation products are a sensitive marker. Monitoring the fibrin‑specific degradation products can be used as an aid to
▪ confirm or refute a tentative diagnosis
▪ estimate the potential risk for patients with existing DIC
▪ monitor an initiated therapy
Apart from DVT, PE, and DIC, D‑Dimer may reflect other causes associated with fibrin formation such as trauma, pregnancy complications, malignant disease or vascular abnormalities. Elevated D‑Dimer levels therefore have to be interpreted in the context of possible underlying diseases and clinical symptoms.
D-dimer values < or =250 ng/mL D-dimer units (DDU) (< or =0.50 mcg/mL fibrinogen equivalent units: FEU) are normal.
Quantitative D-dimer assay result can be reported as either concentration of D-dimer or as FEUs, depending on the calibration method. The two numerical values are easily convertible to each other, since the mass of one unit of fibrinogen-equivalent units (FEU) equals approximately half of one D-dimer unit (DDU):
1 FEU = 2 X DDU
For example, 0.5 µg/mL FEU = 0.25 µg/mL DDU.
SI units Conversion Calculator. Convert D-Dimer level to μg/mL, ng/mL, mg/L, μg/L, μg FEU/mL, ng FEU/mL, mg FEU/L, μg FEU/L. Clinical laboratory units online conversion from conventional or traditional units to Si units. Table of conversion factors for D-Dimer unit conversion to μg/mL, ng/mL, mg/L, μg/L, μg FEU/mL, ng FEU/mL, mg FEU/L, μg FEU/L.