D‐dimer Testing in Clinical Practice in the Era of COVID‐19

D-dimer is a fragment of crosslinked fibrin resulting from plasmin cleavage of fibrin clots and hence an indirect biomarker of the hemostatic system activation. Early in the coronavirus disease 2019 (COVID-19) pandemic, several studies described coagulation disorders in affected patients, including high D-dimer levels. Consequently, D-dimer has been widely used in not-yet-approved indications. Ruling out pulmonary embolism and deep vein thrombosis in patients with low or intermediate clinical suspicion is the main application of D-dimer. D-dimer is also used to estimate the risk of venous thromboembolism recurrence and is included in the ISTH algorithm for the diagnosis of disseminated intravascular coagulation. Finally, numerous studies identified high D-dimer levels as a biomarker of poor prognosis in hospitalized patients with COVID-19. This report focuses on validated applications of D-dimer testing in patients with and without COVID-19.