Characteristics of chronic obstructive pulmonary disease phenotypes based on high-resolution CT and the relationship with interleukin-6

Abstract

To classify the high-resolution CT (HRCT) phenotypes of COPD, and to investigate the clinical characteristics of various phenotypes and the relationship with airway inflammation. Chest HRCT and pulmonary function tests were performed in 84 COPD patients. The patients were classified into 3 phenotypes according to the visual HRCT findings. Exhaled breath condensate was gathered from 30 patients and the interleukin (IL)-6 level was measured by ELISA. The COPD patients were classified into 3 phenotypes: Phenotype A, absence of emphysema, with or without bronchial wall thickening (n = 34); Phenotype E, emphysema without bronchial wall thickening (n = 23); and Phenotype M, emphysema with bronchial wall thickening (n = 27). The 3 phenotypes of COPD showed different characteristics in several aspects. Patients with phenotype A showed a higher body mass index [(25.1 +/- 4.4) kg/m(2) vs phenotype E (22.5 +/- 4.1) kg/m(2) and phenotype M (21.3 +/- 3.4) kg/m(2), F = 6.732, P < 0.01]. The prevalence of patients with milder dyspnea was lower in phenotype A compared with others (15/34) vs phenotype E (2/23) and phenotype M (6/27), chi(2) = 9.097, P < 0.05. The patients who complained of severe expectoration in phenotype E were fewer than those in other groups (0/23) vs phenotype A (2/34) and phenotype M (4/27), chi(2) = 8.702, P < 0.05. The FEV(1)/FVC and FEV(1)% in phenotype M [(53 +/- 14)% and (51 +/- 25)%] were significantly lower as compared with those in other phenotypes [(67 +/- 11)% and (72 +/- 24)% in phenotype A, and (53 +/- 14)% and (52 +/- 26)% in phenotype E], F = 10.252, F = 6.508, P < 0.01. The ratio of inspiratory capacity to total lung capacity (IC/TLC) in phenotype A was higher [phenotype A (41 +/- 17)%, phenotype E (33 +/- 13)%, phenotype M (28 +/- 13)%, F = 5.964, P < 0.01], while the ratio of residual volume to total lung capacity (RV/TLC) was lower [phenotype A (37 +/- 9)%, phenotype E (44 +/- 10)%, phenotype M (45 +/- 8)%, F = 6.954, P < 0.01]. Patients with different phenotypes showed various levels of IL-6 in exhaled breath condensate [phenotype A (19.9 +/- 6.3) ng/L, phenotype E (16.7 +/- 2.1) ng/L, phenotype M (25.6 +/- 4.4) ng/L, F = 7.749, P < 0.01]. Various morphological phenotypes of COPD based on HRCT showed different clinical characteristics and airway inflammation.