To observe the changes in the levels of C-reactive protein (CRP) and procalcitonin (PCT) in serum of patients with acute exacerbations of chronic obstructive pulmonary disease (AECOPD) and to compare with the values of CRP in combination with PCT in the diagnosis and treatment of infective exacerbation of COPD. This evidence concerns the gene CALCA and chronic obstructive pulmonary disease.