Variability in D-dimer reporting revisited

Sir, D-dimers represent a breakdown product of fibrin formation, and D-dimer testing is a common laboratory procedure in haemostasis laboratories. D-dimer testing may be requested in patients as an investigative tool for assessment of venous thromboembolism (VTE), such as deep vein thrombosis (DVT) or pulmonary embolism (PE), typically combined with a pre-test probability score (e.g., Well's score), or else for assessment and potential monitoring of disseminated intravascular coagulation (DIC). Of particular relevance to the current report, is that D-dimer testing has found particular utility as a potential prognostic marker for disease severity in coronavirus disease 2019 (COVID-19), which characterises a pandemic produced by severe acute respiratory syndrome virus coronavirus 2 (SARS-CoV-2). At time of writing, COVID-19 comprised over 17 million confirmed cases, causing nearly 700,000 deaths. The disease expresses various pathophysiological derangements, including (micro) thrombosis, which in turn is associated with various derangements of haemostasis parameters, in particular including D-dimer. As noted, D-dimer also potentially serves as a prognostic marker for severe disease and/or mortality. Thus, it is anticipated that D-dimer testing will increase substantially as clinicians assess and treat increasing numbers of COVID-19 patients.