When we applied the consensus definition by Sin et al. [9] to our study population, the proportion of patients with IgE > 100 IU/mL or positive IgE for D. pteronyssinus tended to be higher in ACO than in non-ACO COPD (68.8% vs 48.0% [P = 0.148] and 37.5% vs 20.0% [P = 0.155], respectively). This evidence concerns the gene IGHE and chronic obstructive pulmonary disease.