d-dimer as a biomarker for COVID-19-associated pulmonary thromboembolism: a narrative review from molecular pathways to the imaging findings

Abstract

Background The coronavirus disease 2019, also known as COVID-19, imposed various challenges to healthcare and became a pandemic accompanied by a high rate of mortality. This infection has many manifestations and affects nearly all body systems. The circulatory and coagulation systems also seem to be affected. Studies show elevated rates of thrombotic events within COVID-19 patients such as disseminated intravascular coagulation (DIC), deep vein thrombosis (DVT), and pulmonary embolism (PE). Incidences of such coagulopathies were correlated to poor patient prognosis and mortality. Given the importance, complication, and mortality caused by thrombotic events (TEs) in COVID-19 patients, the goals of this study are to collect and analyze data on coagulopathy in COVID-19 patients and the pathophysiology and molecular events behind it. We also aim to bring attention to the role of d-dimer in COVID-19 infection by presenting the most recent information available from research studies evaluating d-dimer as a potential biomarker for disease severity, as well as mortality in COVID-19 patients. Main body Various mechanisms are described for COVID-19 coagulopathies such as endothelial cell dysfunction, fibrinolysis inhibitor overexpression, immuno-thrombosis, and imbalance between pro- and anticoagulants, to name a few. d-dimer which is a degradation product of fibrin is a helpful diagnostic tool for the assessment of clots and thrombosis. Given the pro-thrombotic nature of COVID-19 infection, within the current narrative review, we studied the diagnostic value of d-dimer for PE prediction. Several studies utilized d-dimer as a predictive tool for detecting PE, and the results were varied. Different cutoff points are proposed ranging from 0.5 up to over 4 mg/L with varying sensitivity and specificity. Although CT pulmonary angiography (CTPA) is the standard model for the prediction of PE, radiation exposure, contrast nephropathy, higher cost, and lack of adequate access can shift our diagnosis into models based on d-dimer. Short conclusion In summary, various coagulopathies have been associated with COVID-19 infection, and a safe and early diagnosis is needed. d-dimer showed various successes in PE prediction and can be a good candidate for further research and diagnostic model and algorithm development.