CT phenotypes in mild-to-moderate chronic obstructive pulmonary disease: difference before and after the age of 60 years

Abstract

To investigate the pulmonary phenotype of mild-to-moderate chronic obstructive pulmonary disease (COPD) using quantitative computed tomography CT analysis techniques. Sixty-three patients with stable-phase mild-to-moderate COPD and 78 healthy controls, categorised as those aged <60 (28 and 40 patients, respectively) and ≥60 years (35 and 38, respectively), underwent chest low-dose respiratory dual-phase CT and pulmonary function test. Automatic software was used to measure the proximal airway parameters, and the emphysema and air-trapping indices were recorded. The intergroup differences in each parameter were assessed by one-way analysis of variance. At <60 years of age, the mean Pi10WA (Wall area of a hypothetical airway with an internal perimeter of 10 mm) was greater in the mild-to-moderate COPD group than in the healthy control group (17.04±1.63 versus 16.03±1.16 mm2; p=0.004). Mild or moderate air-trapping was observed in the mild-to-moderate COPD group aged <60 years. There was no significant difference in the proximal airway parameters and inspiratory VI-950 (percent voxels less than -950 HU) between the two groups at age ≥60 years (all p>0.05); however, the expiratory VI-856 (percent voxels less than -856 HU) and mean lung density expiratory/inspiratory ratio (MLDE/I) were higher in the mild-to-moderate COPD group than those in the healthy control group (26.02 [30.23] versus 6.45 [11.16]; 0.88±0.05 versus 0.84±0.04; p<0.001 and p=0.024). For patients with mild-to-moderate COPD, the CT phenotype was predominantly the "airway remodelling" type at <60 years of age, and the "air-trapping" type at ≥60 years of age. Thus, pulmonary CT phenotypes of mild-to-moderate COPD patients of different age groups are different.