On the other hand, the elevation of ferritin, procalcitonin and IL11RA by 5-fold, 9-fold and 36-fold in mild COVID-19 cases compared to the healthy control group, and by 1.2-fold, 1-fold and 2-fold in severe COVID-19 cases compared to mild COVID-19 cases, respectively, confirmed that the selected protein panel could be used in COVID-19 severity discrimination (Figure 4). Here, IL11RA is linked to COVID-19.