CXCL8 and chronic obstructive pulmonary disease: The pooled analysis of the relationship between IL-6 and IL-8 levels with COPD pathogenesis suggested that COPD patients showed higher IL-6 (SMD: 0.90; 95%CI: 0.48–1.31; P < 0.001; Fig 3A) and IL-8 levels (SMD: 2.34; 95%CI: 0.69–4.00; P = 0.006; Fig 3B) compared with the controls.