Abstracts

Background: Neutrophil extracellular traps (NETs) are suggested to be the key driver in COVID-19 related immunothrombosis. Increased levels of soluble NETs markers are shown to correlate with COVID-19 severity and outcome. However, limited data is available on the impact of drug therapy on NETs level and the possibility to determine NETs in blood smears. Aims: To determine the possible role of NETs observed in blood smears during COVID-19. Methods: 46 patients with confirmed COVID-19 (11 non-ICU, 26 ICU, 9 ECMO) and 53 healthy volunteers were studied (independent ethics committee of NMRC PHOI No 3/2020). NETs were investigated in standardized thin blood smears produced of citrated whole blood and stained by May-Grunwald-Giemsa method. NETs percentage to number of neutrophils was calculated (%NETs). %NETs median levels between groups are compared using Mann-Whitney U-Test. Results: %NETs was 3.3 times higher in COVID-19 patients compared to healthy donors ( p <0.0001) and 1.3 times higher in ECMO patients ( p <0.0001). Drugs intake was shown to decrease %NETs: tocilizumab -1.6-fold ( P = 0.0066) glucocorticoids -1.2-fold ( P = 0.00087) omeprazole -1.3-fold ( p <0.0001), antibiotic therapy with any antibiotics -1.44-fold ( p <.0001). Interestingly, levofloxacin showed higher decrease in %NETs -1.76-fold. %NETs negatively correlated with platelets refractoriness to activation. %NETs and platelets count were analyzed in those 23 patients (13 deceased), who was observed two last days. %NETs was 2 times higher ( P = 0.47) and the platelets count was 3.3 times lower ( P = 0.0024) in deceased patients. A negative correlation was found between %NETs and platelets count (Spearman ' s correlation R=-0.414 P = .049). Conclusions: COVID-19 severity and outcome correlated with increased level of NETs, determined in blood smears. Intake of several drugs, known to inhibit NETosis or neutrophil activation, lead to decrease of NETs level. Thrombocytopenia and reduced activation capacity of platelets correlated with NETs level, confirming that NETs and platelets together are involved in coagulopathy in COVID-19.