Bronchial inflammation and hyperresponsiveness in well controlled asthma

Abstract

Little research has been devoted to the characteristics of bronchial inflammation in patients with stable, well controlled asthma. The aim of this study was to assess the degree and type of airway inflammation and to investigate the relationship between inflammation and bronchial hyperresponsiveness in patients with well controlled asthma. A cross-sectional study was conducted in 84 adult patients (43 men, mean age 43years) with documented well controlled asthma. Induced sputum samples were obtained and cell types determined by differential cell count. Spirometry and methacholine challenge testing were performed. Asthma Control Questionnaire (ACQ) was used to assess symptoms. Patients were included if their ACQ score was <0.75. A total of 59 patients had persistent bronchial inflammation: 28 cases were considered eosinophilic, 28 neutrophilic, and 3 mixed. Median (range) percentage of eosinophils was 4% (0-64) in patients testing positive to methacholine challenge (n=66) and 1% (0-3) in those testing negative (n=18) (P=0.003). A positive correlation was found between eosinophil percentage and the methacholine dose/response ratio (r=0.477, P=0.0001). The geometric mean (95% CI) of the methacholine PC20 was 1.74mg/mL (1.04-2.93) in patients with eosinophilic inflammation and 4.14mg/mL (2.5-6.84) in those with neutrophilic inflammation (P=0.03). Inflammation and bronchial hyperresponsiveness persist in most patients with well controlled asthma. The study demonstrates that eosinophilic or neutrophilic inflammation persisted in most well controlled asthma patients despite the fact that their condition was controlled and therefore, measurement of bronchial inflammation seems essential to achieve proper asthma control.