Sputum eosinophilia and bronchial responsiveness in patients with chronic non-productive cough responsive to anti-asthma therapy

OBJECTIVE: We aimed to examine airway inflammation and bronchial responsiveness in patients with chronic non-productive cough responsive to anti-asthma therapy. METHODOLOGY: Bronchial responsiveness to methacholine as well as the number of inflammatory cells and concentration of eosinophil cationic protein (ECP) in induced sputum were measured in 42 patients with chronic non-productive cough of unknown origin. Their response to bronchodilator, antiallergic and inhaled or oral glucocorticoid therapy was subsequently assessed. RESULTS: Complete remission of coughing was attained with anti-asthma therapies in 34 patients (responder group), while eight patients did not respond (non-responder group). Twenty patients in the responder group and three in the non-responder group showed bronchial hyperresponsiveness (BHR). The number of eosinophils and ECP levels in the sputum from responders with BHR were significantly increased when compared with those from non-responders and healthy subjects. These sputum measures were also significantly increased in responders without BHR when compared with healthy subjects. However, there were no significant differences in these inflammatory markers between the responders with and without BHR. The neutrophil numbers in the sputum from non-responders and responders both with and without BHR were also significantly higher than in control subjects, but there were no significant differences. CONCLUSIONS: These findings suggest that patients with chronic non-productive cough responsive to anti-asthma therapy characteristically have eosinophilic airway inflammation, which may play an important role in the development of chronic cough. Furthermore, the evaluation of not only bronchial responsiveness but also airway inflammation by examination of induced sputum may be useful for diagnosis and deciding on therapeutic strategies.