IL6 and COVID-19: Severe COVID-19 cases had significantly higher blood level of procalcitonin (SMD = 0.72, 95%CI: 0.34;1,11; P-value: < 0.001; n = 1509), interleukin-6 (SMD = 0.93, 95%CI: 0.25;1.61; P-value: 0.007; n = 875),and C-reactive protein (SMD = 1.34, 95%CI:0.83;1.86; P-value: < 0.001; n = 1974) (Table 2).