GPT and chronic obstructive pulmonary disease: ALT: alanine transaminase; ALP: alkaline phosphatase; AST: aspartate aminotransferase; BMI: body mass index; COPD: chronic obstructive pulmonary disease; CRP: C-reactive protein; DM: diabetes mellitus; GGT: gamma-glutamyl transferase; INR: international normalized ratio; LDH: lactate dehydrogenase; PTT: partial thromboplastin time; PT: prothrombin time; WBC: white blood cell