S100A9 as an inflammatory marker in hospitalized COVID-19 patients

Objective: To evaluate serum levels of S100A9 as an inflammatory marker of unfavorable outcomes in patients with COVID-19 in a cross-section study. Material: Participants in this study were allocated from reference care units for the diagnosis of COVID-19 in the western region of Bahia, Brazil, from May 2020 to June 2021. Methods: Blood samples were collected from control group, patients with RT-qPCR positive for COVID-19 with different clinical manifestations of the disease and cured COVID-19 patients. Cytokines and inflammatory mediators (S100A9, D-dimer IL-6, IL-10, TNF-a, IL-12p70) were analyzed by ELISA/CBA. Results: : Hospitalized COVID-19 patients presented increased production of S100A9, IL-6, IL-10, TNF-α, IL-12p70, and D-dimer when compared with not hospitalized patients, not infected or cured. Spearman analysis revealed a positive correlation between S100A9 and inflammatory cytokines/D-dimer. ROC curve analyses demonstrated accurate sensitivity and specificity for S100A9 and IL-6. Conclusion: S100A9 serum levels were elevated in hospitalized patients associated with unfavorable outcomes and poor prognosis in COVID-19. Thus, using S100A9 in association with other standardized parameters in clinical protocols may be a useful tool to predict critical clinical evolution during SARS-COV-2 infection.