CXCL8 and chronic obstructive pulmonary disease: Moderate-quality evidence indicates that elevated levels of CRP, procalcitonin (PCT), interleukin-8 (IL-8), and tumor necrosis factor-α (TNF-α) are associated with bacterial infection in acute exacerbations of COPD (AECOPD) [10], while higher CRP concentrations predict an increased risk of hospital readmission [11].