D-Dimer is contained in the soluble derivatives formed upon plasmin degradation of Factor XIIIa cross-linked fibrin (XDP). Plasmin, a serine protease, when free from inhibitors digests the insoluble cross-linked fibrin yielding a variety of soluble derivatives. Their molecular weights depend on the extent of the digestion. These soluble fibrin degradation products contain a neoantigen (D-Dimer domain) which is not present on the original fibrinogen molecule, its degradation products or on soluble fibrin. The determination of D-Dimer is becoming a widespread tool for diagnosing thrombosis and monitoring thrombolytic therapy.
Elevated levels of D-Dimer are found in clinical conditions such as deep vein thrombosis (DVT), pulmonary embolism (PE) and disseminated intravascular coagulation (DIC). DDimer levels also rise during the normal pregnancy but very high levels are associated with complications.
A negative D-Dimer result when combined with a clinical assessment of low pretest probability has been shown to have a high negative predictive value for DVT or PE.