Biomarker profiles associated with COVID-19 severity and mortality

Introduction: SARS-Cov-2 virus can cause a release of pro-inflammatory cytokines after infection of the upper and lower respiratory tract. The aim of this study was to analyze biomarkers that might predict the severity and progression of the disease both in the acute phase of the infection and after recovery from COVID-19 hospitalization. Methods: Patients with COVID-19 pneumonia requiring hospital (n = 48) or ICU admission (n = 41) were included in the study. At the time of admission, and after one and six months of COVID-19 negative results, a clinical study, lung function tests, blood extraction and chest CT scan were performed. Blood samples were drawn to measure different cytokines and lung fibrosis biomarkers. Results: Increased levels of IFN- ɣ and TNF-α were observed during infection. Higher IL-4, IL-5 and IL-6 levels (p = 0.039, 0.011 and 0.045 respectively) were recorded in patients who required ICU admission (Group 2) than in those who were admitted to the ward (Group 1). IL-17 and IL-8 levels were higher in patients in the ward at the moment of admission (p = 0.026 and 0.001 respectively). IL-7 and MCP-1 levels increased in both groups one month after the infection. YKL-40 and KL-6 levels were higher in patients who died. Conclusions: Patients who required ICU admission had higher levels of Th2 cytokines, while patients admitted to the ward showed an innate immune response activation with IL-8 release and Th1/Th17 lymphocyte contribution. Increased levels of YKL-40 and KL-6 were associated with mortality in COVID-19 patients. Study funded by Air liquid.