The serum levels of nearly all analyzed chemokines and growth factors (excluding MIP-1β) were higher in stage 2 than stage 1 patients (Figure 5), which suggests that the analyzed chemokines, in particular GM-CSF, basic-FGF and MIG, have high diagnostic value (AUC of 0.7116, 0.7324 and 0.7763, respectively) and can be used as effective markers for monitoring disease severity in COVID-19 patients. The gene discussed is CXCL9; the disease is COVID-19.