Identification of Subtypes of Refractory Asthma in Korean Patients by Cluster Analysis
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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.
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.
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.
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.
KeywordsAsthma Cluster analysis Airway obstruction Bronchial hyperreactivity
American Thoracic Society
Body mass index
Chronic obstructive pulmonary disease
European Network for Understanding Mechanism of Severe Asthma
Forced expiratory volume in 1 s
Forced vital capacity
Global Initiative for Asthma
- PC20 M
Methacholine concentration that induced a 20 % decline of FEV1 from baseline FEV1
Quality of life
Severe Asthma Research Program
The Epidemiology and Natural history of asthma: Outcomes and treatment Regimens
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.
Conflict of interest
The authors have no conflicts of interest to disclose.
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