CD66b+/CD68+ circulating extracellular vesicles, lactate dehydrogenase and neutrophil‐to‐lymphocyte ratio can differentiate coronavirus disease 2019 severity during and after infection

Abstract Coronavirus disease 2019 (COVID‐19) has been a major public health burden. We hypothesised that circulating extracellular vesicles (cEVs), key players in health and disease, could trace the cell changes during COVID‐19 infection and recovery. Therefore, we studied the temporal trend of cEV and inflammatory marker levels in plasma samples of COVID‐19 patients that were collected within 24 h of patient admission (baseline, n = 80) and after hospital discharge at day‐90 post‐admission (n = 59). Inflammatory markers were measured by standard biochemical methods. cEVs were quantitatively and phenotypically characterized by high‐sensitivity nano flow cytometry. In patients recovered from COVID‐19 lower levels of inflammatory markers were detected. cEVs from vascular (endothelial cells) and blood (platelets, distinct immune subsets) cells were significantly reduced at day‐90 compared to admission levels, a pattern also observed for cEVs from progenitor, perivascular and epithelial cells. The best discriminatory power for COVID‐19 severity was found for inflammatory markers lactate dehydrogenase and neutrophil‐to‐lymphocyte ratio and for granulocyte/macrophage‐released CD66b+/CD68+‐cEVs. Albeit inflammatory markers were good indicators of systemic inflammatory response and discriminators of COVID‐19 remission, they do not completely reveal cell stress and organ damage states. cEVs reaching baseline pre‐infection levels at 90 days post‐infection in recovered patients discriminate parental cells affected by disease.