IL6 and chronic obstructive pulmonary disease: COPD: Chronic obstructive pulmonary disease, TLC: Total leukocyte count, NLR: Neutrophil-lymphocyte ratio, AST: Aspartate aminotransferase, ALT: Alanine aminotransferase, ALP: Alkaline phosphatase, CRP: C-reactive protein, IL-6: Interleukin 6, LDH: Lactate dehydrogenase, ULN: Upper limit of normal