Eosinophilia at the time of respiratory syncytial virus bronchiolitis predicts childhood reactive airway disease

Objective. Bronchiolitis in infancy is viewed as a risk factor for childhood asthma, but factors predicting which infants will have persistent wheezing have not been identified. In addition, the nature of the association between the 2 conditions is uncertain. We wished to determine whether eosinophil counts at the time of acute bronchiolitis predicted the presence of wheezing in later childhood. Methods. We retrospectively identified infants hospitalized with bronchiolitis, determined peripheral blood eosinophil counts at the time of bronchiolitis, and then contacted their families when they had reached 7 years of age. Results. Eosinophil counts at the time of bronchiolitis were greater in subjects who would have wheezing at 7 years of age (median: 98 cells/mm³) than in infants who would have no recurrent wheezing (median: 0 cells/mm³) or transient wheezing only up to 3 years of age (median: 0 cells/mm³). When the effects of family history of asthma, gender, and passive exposure to cigarette smoke were examined, only eosinophilia at the time of bronchiolitis demonstrated a statistically significant relationship to the presence of wheezing at 7 years of age. Conclusions. Eosinophilia at the time of bronchiolitis generally predicts the development of wheezing persisting into later childhood. Therefore, the association of bronchiolitis and childhood asthma seems more likely to be attributable to an immunologic anomaly that precedes the development of, or is induced by, bronchiolitis rather than to structural damage to the airway as a result of bronchiolitis.