CST3 and chronic obstructive pulmonary disease: A pairwise comparison revealed a statistically significant difference between cystatin C levels in patients with hypertension (Group I) and those with COPD (Group III): 1.16 (1.03; 1.27) mg/l and 1.05 (0.96; 1.05) mg/l respectively (p=0.02), and between patients with comorbid pathology of hypertension and COPD (Group II) and those with COPD (Group III): 1.3 (1.22; 1.38) mg/l and 1.05 (0.96;1.05) mg/l (p=0.006) respectively (Table 3, Figure 1).