The Phenotypes of Asthma-Bronchiectasis Overlap: Clinical Characteristics and Outcomes

Asthma-bronchiectasis overlap (ABO) encompasses heterogeneous manifestations, which may predict distinct clinical outcomes. We sought to identify the clinical phenotypes of ABO and compare them to asthma alone or bronchiectasis alone. In this retrospective cohort study, we extracted electronic medical records from 292 inpatients with ABO, 901 inpatients with asthma alone, and 1,192 inpatients with bronchiectasis alone who were hospitalized between 2015 and 2020. We phenotyped ABO using 2-step unsupervised clustering analysis by using an independent cohort (n = 76). Compared to asthma or bronchiectasis alone, ABO exhibited greater disease severity and worse clinical outcomes. We identified 3 ABO phenotypes: asthma-dominant ABO (ABO-A, n = 100) with more prominent asthma symptoms; bronchiectasis-dominant ABO (ABO-B, n = 89) with more pronounced features of bronchiectasis; and co-existence of asthma and severe bronchiectasis (ABO-S, n = 103) with worse clinical outcomes. Compared to ABO-B, both ABO-A and ABO-S were associated with significantly higher blood neutrophil ratios (55.8% vs. 59.1% vs. 64.4%, P < 0.001), poorer lung function (FEV1% predicted: 79.1% vs. 67.5% vs. 50.1%, P < 0.001), longer hospital stay (6.0 vs. 7.0 vs. 7.0 days, P = 0.004), and higher risks of hospitalization within the next 2 years (ABO-A: hazards ratio [HR], 3.76, 95% confidence interval [CI], 1.12-12.62, P = 0.032; ABO-S: HR, 4.05, 95% CI, 1.14-14.36, P = 0.031). The radiologic severity of bronchiectasis and the use of systemic corticosteroids can identify the clinical phenotypes of ABO. The heterogeneity of clinical manifestations may help formulate personalized management strategies and predict the prognosis of ABO.