The Reply

We thank Dr Zalmay et al for giving us the opportunity to respond to their concerns. The aim of our study¹ was to examine the diagnoses and outcomes of acute medical patients with an elevated D-dimer. Our results confirm that patients with normal D-dimer levels are unlikely to die within 90 days, and that elevated D-dimer levels are not only associated with an increased risk for venous thromboembolism, but are also associated with infection, cancer, heart failure, and anemia. Our results confirm that D-dimer is a nonspecific test, and therefore, is of little diagnostic value in an unselected patient population, but is of prognostic value. This leads us to speculate, but not conclude, that D-dimer could be used as a prognostic marker. The main concern against routine measurement of D-dimers on every emergency department patient is that it would result in superfluous downstream investigations. However, in an observational trial during the current COVID-19 pandemic, in which a third of Danish emergency departments participated, routine measurement of D-dimers in more than 500,000 visits did not result in increased unnecessary radiological investigations.² We, of course, agree with Zalmay et al that the jury is still out on routine use of the D-dimer in acute medical illness, and that large multicenter trials will be needed to prove that routine D-dimer measurement leads to improved outcomes.