Observational study of the natural history of eosinophilic bronchitis

Background Eosinophilic bronchitis is an important cause of chronic cough. Treatment with inhaled corticosteroids is associated with a short-term improvement in cough and reduced sputum eosinophil count but the long-term outcome is uncertain. Objective To determine the long-term outcome in patients diagnosed with and treated for eosinophilic bronchitis. Methods We have performed a longitudinal study of symptoms, eosinophilic airway inflammation, spirometry and airway hyper-responsiveness in all patients diagnosed with eosinophilic bronchitis over 7 years. Results We identified 52 patients with eosinophilic bronchitis and longitudinal data of greater than 1 year (mean 3.1 years) was available in 32 patients, all of whom were treated with inhaled steroids. Three (9%) patients developed symptoms consistent with asthma and a methacholine PC20 < 8 mg/mL on one or more occasion. Five (16%) patients developed fixed airflow obstruction defined by a persistent post-bronchodilator forced expiratory volume in 1 s (FEV1)/forced vital capacity < 70%. One (3%) patient had complete resolution of symptoms and eosinophilic airway inflammation off treatment. The remaining patients had ongoing eosinophilic airway inflammation and/or continuing symptoms. Multiple linear regression identified smoking, female gender and area under the curve of sputum eosinophil count over time as the most important predictors of decline in FEV1. Conclusions The most common outcome in eosinophilic bronchitis is continuing disease and complete resolution is rare. Asthma and fixed airflow obstruction developed in relatively few patients. The most important factors associated with a more rapid decline in FEV1 were female gender, smoking and prolonged eosinophilic airway inflammation.