Neutrophilic and eosinophilic inflammation in bronchiolitis and long-term respiratory sequelae

Risk factors for bronchiolitis and recurrent wheezing episodes remain unclear. Neutrophil or eosinophil counts at the time of hospitalization for bronchiolitis may play an important role.

To study the correlation between blood neutrophil and eosinophil levels in patients with bronchiolitis, recurrent wheezing episodes and lung function.

We followed 645 children hospitalized for bronchiolitis during nine consecutive seasons for six years. Clinical and laboratory information was obtained from medical records and a standardized questionnaire was used to collect demographic data. Parents were interviewed annually after hospitalization to check for recurrent wheezing episodes. We considered patients with more than two wheezing episodes at follow-up to be positive. We divided the population into two groups based on the 75th percentile for neutrophil circulating count at the time of bronchiolitis: <6000/μL (group 1) and >6000/μL (group 2). We studied also eosinophils blood level at hospitalization and we correlated this data with follow-up. At 6 years of age 253 performed spirometry.

group 2 had a higher probability of wheezing at 12 and 36 months post bronchiolitis (59.6 % vs 49.6 %, p = 0.05; 46.2 % vs 33.1 %, p = 0.01). No differences were found at 24, 48, 60 and 72 months after bronchiolitis. Spirometry performed at 6 years of age did not show significant differences between the two groups. No differences were found between patients with positive follow-up at 12, 24, 36, 48, 60 and 72 months and eosinophils blood levels.

Neutrophil inflammation was associated with preschool wheezing in the first 36 months after the disease.