D-dimer in Coronavirus 2019: An Acute Phase Reactant?

D-dimers are released following the breakdown of blood clots, essentially representing a byproduct of the degradation of fibrin by plasmin activity. Normal values are less than 0.50 mg/L (in fibrinogen equivalent units), and the negative predictive values of D-dimer measurements are excellent to rule out pulmonary embolism, deep vein thrombosis, and disseminated intravascular coagulation, since it would otherwise increase substantially in those settings. However, the D-dimer assay only represents a screening test and should be interpreted in the context of the patient’s clinical signs and symptoms.[1] Overt coagulation abnormalities are common in patients with coronavirus disease 2019 (COVID-19) and have led to an increase in requests of laboratory biomarkers, such as blood cell counts, acute phase reactants, coagulation tests, and platelet function assays, as aids in the clinical decision-making processes throughout the pandemic.[2] [3] D-dimer levels are among the most frequently and thoroughly studied, and the International COVID-19 Thrombosis Biomarkers Colloquium concluded that they were associated with patient prognosis and were helpful in clinical decision-making in patients requiring imaging studies, in the administration of thromboprophylaxis, and to detect and prevent complications.[4] While the consensus suggests that an elevated D-dimer is associated with worse disease outcomes,[5] the literature is not consistent in terms of whether the increase in D-dimer in COVID-19 can predict thrombotic events. Moreover, some issues have been identified in various publications, whereby comparisons between studies reporting D-dimer levels in different hospital units only reach confusing conclusions on their clinical significance.[6]