Impulse oscillometry-defined airway abnormalities as a treatable trait for mild-to-moderate COPD: a prospective cohort study with 3-year follow-up

Background Treatable traits (TTs) can effectively conduct personalised assessment and treatment for patients with mild-to-moderate COPD. After excluding the classic TTs, do some neglected TTs remain? We evaluated associations of impulse oscillometry (IOS)-defined airway abnormalities (AAs) with respiratory health outcomes and prognoses in patients with mild-to-moderate COPD. Methods We analysed the baseline and 3-year follow-up data from a prospective cohort in China. Patients with mild-to-moderate COPD were enrolled with excluded classic TTs (COPD Assessment Test ≥10, modified Medical Research Council score ≥2, frequent acute exacerbations (AEs) and forced expiratory volume in 1 s (FEV 1 ) % pred <60%). AAs were defined based on IOS parameter resonant frequency greater than the upper limit of normal. Differences in lung function decline and AEs were examined among groups with normal spirometry, AAs and without AAs in patients with mild-to-moderate COPD. Results 1328 participants were finally enrolled (799 normal spirometry, 230 without AAs and 299 with AAs in mild-to-moderate COPD). The AA group was older and exhibited worse lung function, higher symptom scores and worse image abnormalities than the other groups. During the 3-year follow-up, compared with the group with normal spirometry, a faster FEV 1 decline and a higher risk of total AEs were observed in the AA group, but no differences in FEV 1 decline and total AEs were found in groups with normal spirometry and the group without AAs. Conclusion The AA group in mild-to-moderate COPD experienced worse image abnormalities, a higher risk of AEs and a faster FEV 1 decline. These results suggest that AAs may be a special TT in patients with mild-to-moderate COPD.