Abstract
Background
Refractory asthma, a subtype of asthma with uncontrolled symptoms despite antiasthma medications, is a heterogeneous syndrome with variable clinical features, presumably different etiologies, and pathophysiological mechanisms. The heterogeneity of refractory asthma, however, is poorly understood. We aimed to characterize refractory asthma and to improve our understanding of the heterogeneity of refractory asthma patients.
Methods
We identified refractory asthma patients (n = 96) as defined by the American Thoracic Society’s criteria from a cohort of Korean asthma patients (n = 2,187). Then, cluster analysis was conducted to classify subtypes of refractory asthma.
Results
Among the study group, 4.4 % (n = 96) of all asthma patients had refractory asthma. Cluster analysis identified four distinct groups of refractory asthma. Age at onset was younger in clusters 1 and 2 than in clusters 3 and 4. Patients in cluster 1 had the most well-preserved pulmonary function; patients in cluster 2 had a female predominance and the most severe airway obstruction; patients in cluster 3 were mostly female and had the most enhanced bronchial hyperresponsiveness; and patients in cluster 4 were most male and tended to be cigarette smokers.
Conclusions
The current results suggest that refractory asthma is a heterogeneous syndrome and could be classified into four subtypes. Underlying pathogenesis and therapeutic approaches may differ for the different subtypes and further research is needed.
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Abbreviations
- ATS:
-
American Thoracic Society
- BHR:
-
Bronchial hyperresponsiveness
- BMI:
-
Body mass index
- COPD:
-
Chronic obstructive pulmonary disease
- ENFUMOSA:
-
European Network for Understanding Mechanism of Severe Asthma
- FEV1 :
-
Forced expiratory volume in 1 s
- FVC:
-
Forced vital capacity
- GINA:
-
Global Initiative for Asthma
- ICS:
-
Inhaled corticosteroid
- LABA:
-
Long-acting beta-agonist
- PC20 M:
-
Methacholine concentration that induced a 20 % decline of FEV1 from baseline FEV1
- QOL:
-
Quality of life
- SARP:
-
Severe Asthma Research Program
- TENOR:
-
The Epidemiology and Natural history of asthma: Outcomes and treatment Regimens
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Acknowledgments
This study was supported by grants from the Korea Health 21 R&D Project, Ministry of Health, Welfare and Family Affairs (A090548 and A040153), Republic of Korea, to CSP, HBM, and YSC.
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The authors have no conflicts of interest to disclose.
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A. S. Jang and H.-S. Kwon contributed equally to this study.
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Jang, A.S., Kwon, HS., Cho, Y.S. et al. Identification of Subtypes of Refractory Asthma in Korean Patients by Cluster Analysis. Lung 191, 87–93 (2013). https://doi.org/10.1007/s00408-012-9430-8
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DOI: https://doi.org/10.1007/s00408-012-9430-8