Heterogeneity of paucigranulocytic asthma: A prospective cohort study with hierarchical cluster analysis

Ke Deng, Xin Zhang, Ying Liu, Li Zhang, Gang Wang, Min Feng, Brian G Oliver, Lei Wang, Philip M Hansbro, Lin Qin, Min Xie, Zhi Hong Chen, Jodie Simpson, Jie Zhang, Wei Min Li, Gang Wang, Peter Gerard Gibson
Journal of Allergy and Clinical Immunology in Practice 2021 January 19

BACKGROUND: Asthma, a heterogeneous disease, can be divided into four inflammatory phenotypes using induced sputum cell counts -eosinophilic asthma (EA), neutrophilic asthma (NA), mixed granulocytic asthma (MGA), and paucigranulocytic asthma (PGA). While research has focused on EA and NA, there is little known on PGA.

OBJECTIVE: To study the heterogeneity of PGA, and identify possible PGA clusters to guide clinical treatment.

METHODS: Patients with PGA were grouped by hierarchical cluster analysis, and enrolled into a prospective cohort study to validate the clusters, relative to future risk of asthma exacerbations in a real-world setting. Clusters were validated by tree analysis in a separate population. Finally, we explored PGA stability.

RESULTS: Cluster analysis of 145 patients with PGA identified three clusters: Cluster 1 (n = 110, 75.9%) was "mild PGA," Cluster 2 (n = 20, 13.8%) was "PGA with psychological dysfunction and rhinoconjunctivitis and other allergic diseases," and Cluster 3 (n = 15, 10.3%) was "smoking-associated PGA." Cluster 3 had significantly increased risk of severe exacerbation (RR = 6.43, P = 0.01), emergency visit (RR = 8.61, P = 0.03), and hospitalization (RR = 12.94, P < 0.01). Results of the cluster analysis were successfully validated in an independent PGA population classified using decision tree analysis. Although PGA can transform into or develop from other phenotypes, 70% were stable over time.

CONCLUSIONS: Among three identified PGA clusters, Cluster 3 had a higher risk of severe exacerbation. PGA heterogeneity indicates the requirement of novel targeted interventions.

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