CXCL8 and chronic obstructive pulmonary disease: For the baseline assessments, six biomarkers showed weak correlation with COPD disease severity as defined by GOLD stage: β-defensin-2 (r = 0.2, p = 0.005), IL-8 (r = 0.15, p = 0.043), MMP-8 (r = 0.19, p = 0.007), MMP-9 (r = 0.16, p = 0.024), adiponectin (r = 0.18, p = 0.009) and hepatocyte growth factor (r = -0.21, p = 0.003).