Disseminated intravascular coagulation (DIC) is common. It is seen in approximately 1% of admissions at larger hospitals. About 83% of patients with bacterial sepsis experience DIC and as many as 31% of trauma victims will undergo DIC.
Patients in DIC will have prolongation of their PT and aPTT. Measuring fibrinogen levels was initially thought to be useful in the diagnosis of DIC. However, fibrinogen is an acute phase reactant, which means its concentration increases during inflammation. This can make fibrinogen difficult to assess as its increase may be due to an underlying inflammatory condition and not DIC. In DIC, a normal fibrinogen level can occur in >57% of cases. A better marker for DIC would be a test that directly measures FDP. There are many different types of fibrin degradation products. One specific product is composed of 2 'D' domains of fibrin and one 'E' domain. This protein product is referred to as a d-dimer.
The d-dimer test is a plasma test that can be measured quickly in the lab using automated immunoassays. The d-dimer is increased in both acute and chronic DIC. A normal d-dimer test effectively rules out DIC (it has a very good negative predictive value). But it is a low-specificity test since elevations also occur in other conditions (e.g., pregnancy, venous thromboembolism, and malignancy).
