Clinical features of patients with paucigranulocytic asthma classified based on the induced sputum test

ABSTRACT

Purpose@#Asthma phenotypes are often defined by relative cell counts of airway granulocytes. Induced sputum test results enable clinicians to determine the inflammatory phenotype of asthma based on the eosinophil and neutrophil counts. This study aimed to investigate clinical characteristics of patients with asthma according to the inflammatory phenotype of their condition. @*Methods@#Data from 107 patients with asthma reported at a single tertiary allergy center in Korea during October 2016 to January 2019 were obtained. Patients were categorized into 4 asthma phenotypes based on the cell counts on the induced sputum test eosinophilic, neutrophilic, mixed, and paucigranulocytic types. Blood eosinophil count, total IgE level, eosinophil cationic protein, spirometric measurements, fractional exhaled nitric oxide, atopy based on the skin prick test, PC20 (provocative concentration of methacholine causing a 20% fall in forced expiratory volume in 1 second) in methacholine provocation test, type of asthma controller used, frequency of exacerbation, and use of systemic corticosteroids were examined. @*Results@#The frequency of phenotype is as follows eosinophilic (21.4%), neutrophilic (34.8%), mixed (13.4%), and paucigranulocytic types (30.4%). During the observation period, the proportion of patients who experienced an exacerbation and received systemic glucocorticosteroids were significantly lower in patients with the paucigranulocytic type of asthma than in those with the mixed type of asthma (6.3% vs. 40.0%; P = 0.007 and 5.9% vs. 40.0%; P = 0.004, respectively). @*Conclusion@#Paucigranulocytic asthma may be associated with lower incidence rates of asthma exacerbation and systemic corticosteroid use than the other phenotypes, classified according to induced sputum test results.