Three of these markers showed a significant difference (FDR adjusted p-value <0.05) for all smoker groups (COPD and CS) vs. non-smoker groups (NS and FS) comparisons: alpha-1-antitrypsin (AAT), haptoglobin, and intercellular adhesion molecule 1 (ICAM-1). This evidence concerns the gene HP and chronic obstructive pulmonary disease.