The proportion of patients with high serum EDN and YKL-40 levels was significantly higher in ACO than in asthma or COPD: odds ratio, 3.85 (95% CI, 2.35–6.36); p < 0.001; sensitivity, 45.2%; specificity, 82.4%. This evidence concerns the gene CHI3L1 and chronic obstructive pulmonary disease.