Clinical spectrum of COVID-19 patients and decreased serum level of miR-146a as a sign of inflammation

Background There is increasing evidence that inflammation is an important determinant in COVID-19 pathogenesis. Several studies describe cytokines and microRNAs as important regulators of immune and inflammatory responses in other diseases, regarding them as valuable biomarkers. Aim Identify a potential relationship between cytokines (interleukin [IL]-6, IL-8) and microRNAs (miR-146a-5p, miR-155-5p) and clinical characteristics of COVID-19 patients, focusing on disease severity and mortality risk. Methods Serum expression levels of miR-146a, miR-155, IL-6, IL-8, C-reactive protein, ferritin, and neutrophil-to-lymphocyte ratio, of 25 mild, 73 moderate, and 39 severe COVID-19 patients from Quito-Ecuador, were determined to correlate outcomes with clinical parameters. Results In all groups, overweight and obesity were the most prevalent comorbidities (75.91%). Serum levels of IL-6 were significantly elevated in patients with moderate and severe COVID-19 (analysis of variance [ANOVA] p ≤ 0.000). miR-146a was significantly decreased in moderate and severe COVID-19 patients when compared with mild cases (ANOVA p = 0.002). ROC curve analysis showed that selected cut-off values for miR-146a > 3.999 ΔCt for mild vs moderate condition (sensitivity 83.56%, specificity 48%) and miR-146a > 3.999 ΔCt for mild vs severe condition (sensitivity 84.62%, specificity 40%), and IL-6 ≥ 72.25 pg/mL (sensitivity 78.95%, specificity 60.61%) when combined with clinical pretest probability, can be used to predict aggravation and death in COVID-19 patients. Odds ratios (ORs) of miR-146a (OR = 4.322) and IL-6 (OR = 3.198) indicate an increased risk of worsening and death, respectively, when cut-off points were taken into consideration. Conclusion This study shows that elevated inflammatory IL-6 and decreased serum levels of anti-inflammatory miR-146a-5p can be discriminatory markers of COVID-19 severity and mortality.