Flow cytometric evaluation of the neutrophil compartment in COVID‐19 at hospital presentation: A normal response to an abnormal situation

Coronavirus disease 2019 (COVID‐19) is a rapidly emerging pandemic disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2). Critical COVID‐19 is thought to be associated with a hyper‐inflammatory process that can develop into acute respiratory distress syndrome, a critical disease normally mediated by dysfunctional neutrophils. This study tested the hypothesis whether the neutrophil compartment displays characteristics of hyperinflammation in COVID‐19 patients. Therefore, a prospective study was performed on all patients with suspected COVID‐19 presenting at the emergency room of a large academic hospital. Blood drawn within 2 d after hospital presentation was analyzed by point‐of‐care automated flow cytometry and compared with blood samples collected at later time points. COVID‐19 patients did not exhibit neutrophilia or eosinopenia. Unexpectedly neutrophil activation markers (CD11b, CD16, CD10, and CD62L) did not differ between COVID‐19‐positive patients and COVID‐19‐negative patients diagnosed with other bacterial/viral infections, or between COVID‐19 severity groups. In all patients, a decrease was found in the neutrophil maturation markers indicating an inflammation‐induced left shift of the neutrophil compartment. In COVID‐19 this was associated with disease severity. Graphical COVID‐19 is associated with a decrease in maturation markers in the neutrophil compartment without clear signs of activation at hospital presentation (figure made with the use of Biorender software).