CST3 and chronic obstructive pulmonary disease: We show that the differences in plasma levels of cathepsin S and cathepsin S/cystatin C ratios between the COPD patients and the control groups were not due to differences in BMI, and prevalence of cardiovascular disease, as assessed by measuring the diameters of the abdominal aorta and main pulmonary artery, systemic hypertension, or renal dysfunction, as assessed by serum creatinine levels.