Will nonasthmatic eosinophilic bronchitis develop chronic airway obstruction?: A prospective, observational study.

The long-term prognosis of nonasthmatic eosinophilic bronchitis (NAEB) is still unclear. This study aims to observe the frequency of relapse among NAEB patients and the likelihood of developing into chronic airflow obstruction over time.The eligible patients with NAEB from 2003 to 2013 were followed up for at least 1 year. During the follow-up period, we collected the patients' clinical symptoms, sputum eosinophil count, spirometry and bronchial hyperresponsiveness for evaluation. Linear mixed model was adopted to determine the relationship between time and lung function.A total of 234 patients with NAEB were identified, of whom 141 were followed up for over one year with the median period of 4.1 years. Up to 59.6% patients had relapse after treatments. Both allergic rhinitis (OR 4.37, 95%CI 1.049～18.203, P=0.043) and sputum eosinophilia after 4-week treatment with inhaled corticosteroids (OR 9.493, 95%CI 2.381～37.850, P=0.001) were risk factors for relapse. Among the 141 patients, eight of them (5.7%) developed mild asthma. During the follow-up period, no progressive decline in FVC, FEV1, FEV1/FVC were observed (P>0.05). Although the proportion of small airway dysfunction (MMEF<65%）significantly increased at the last visit in all groups (all P<0.05), only relapse group showed MMEF decline at the end of follow-up (P<0.05) in linear mixed model.Over 50% patients with NAEB have repeated episodes associated with persistent sputum eosinophilia after treatment and allergic rhinitis. In our cohort, chronic airway obstruction does not develop despite small airway dysfunction increases over time.