IL6 and bacterial infectious disease: The serum concentrations of C-reactive protein (CRP) (SMD = 0.39, 95% CI 0.02–0.76), procalcitonin (SMD = 1.95, 95% CI 1.32–2.59) and tumor necrosis factor-alpha (TNF-α) (MD = 0.31, 95% CI 0.25–0.38) in the G (−) bacterial infection group were significantly higher than those in the G (+) bacterial infection group, but there was no significant difference in IL-6 (SMD = 1.33, 95% CI − 0.18–2.84) and WBC count (MD = − 0.15, 95% CI − 0.96–00.66).