The performance of the CRP level in differentiating patients with severe or very severe COPD from those with mild or moderate COPD was as follows: AUC = 0.775 (95% CI: 0.64–0.90, p = 0.001 < 0.05), with an optimal cut-off of 12.25 mg/L, showing a sensitivity of 95.7% and a specificity of 71.9%. This evidence concerns the gene CRP and chronic obstructive pulmonary disease.