GDF15 and COVID-19: Among others, calprotectin (70, 71), endocan (72), growth differentiation factor 15 (GDF15) (73), inflammatory cytokines (IL1 and IL6) (74), miRNAs (75), neopterin (76), soluble suppressor of tumorigenicity 2 (sST2) (77), and T cell immunoglobulin and mucin domain containing protein 3 (Tim) (78) have been reviewed having the potential as biomarkers for COVID-19 severity.