Evidence for two clusters among non-eosinophilic asthmatics.

[en] BACKGROUND: Although asthma is often seen as an eosinophilic disease associated with atopy non eosinophilic asthmatics represent a substantial part of asthmatic population.
OBJECTIVE: Here we have applied an unsupervised clustering method on a cohort of 588 non eosinophilic asthmatics (sputum eosinophils <3%) recruited from an asthma clinic of a secondary care center.
METHODS: Our cluster analysis of the whole cohort identified two subgroups as cluster 1 (n=417) and cluster 2 (n=171).
RESULTS: Cluster 1 consisted of a dominant female group with a late disease onset, a low proportion of atopy (24%) and a substantial smoking history (53%). In this cluster, treatment burden was low (<50% of ICS users), asthma control and quality of life was poor with median ACT, ACQ and AQLQ of 16 and 1,7 and 4,5 respectively whereas lung function was preserved with a median post bronchodilation FEV1 of 93% predicted. Cluster 2 was a dominant male group, almost exclusively composed of atopic patients (99%) with early disease onset and a moderate treatment burden (median ICS dose 800 µg/d equivalent beclomethasone). In cluster 2 asthma was partially controlled with median ACT and ACQ reaching 18 and 1.3 respectively and lung function well preserved with a median post bronchodilation 95% predicted. While systemic and airway neutrophilic inflammation was the dominant pattern in cluster 1, cluster 2 essentially comprised paucigranulocytic asthma with moderately elevated FeNO.
CONCLUSION: Non eosinophilic asthma splits in two clusters distinguishing by disease onset, atopic status, smoking history, systemic and airway inflammation and disease control and quality of life.