More on Persistent Endotheliopathy in the Pathogenesis of Long COVID Syndrome.

We are grateful for the comments and the interesting additional novel data presented by von Meijenfeldt et al [1]. These findings provide further evidence that sustained endotheliopathy and coagulopathy are both common in patients following acute COVID-19 [2-5]. The longitudinal data presented provide additional insights into the duration of specific aspects of COVID-19-induced hemostatic dysfunction. Previous studies have reported elevated D-dimer levels in 25% of patients in the first few months post-SARS-CoV-2 infection [2, 5]. Notwithstanding differences in patient cohorts and study design, von Meijenfeldt et al show that these elevated D-dimer levels after acute COVID appear to normalize by 4 months [1]. Given that convalescent COVID-19 patients commonly present with respiratory symptoms, this observation has important clinical implications with respect to the utility of D-dimer testing in pulmonary embolism testing algorithms.