224 Blood Eosinophils, Immunoglobulin E, and Bronchiolitis Severity

Bronchiolitis is the leading cause of hospitalization for US infants. Despite ongoing research, there are currently no effective targeted therapies for treatment of bronchiolitis. Previous studies have shown higher blood eosinophil levels and higher immunoglobulin E (IgE) levels are associated with higher bronchiolitis severity. The aim of this study was to investigate the association between blood eosinophil and IgE levels at time of hospitalization and acute severity among infants hospitalized for bronchiolitis. We performed a 17-center, prospective cohort study from 2011 to 2014. Children <1-year old hospitalized with a physician diagnosis of bronchiolitis were enrolled. Of the 1016 children in the cohort, 880 (87%) had eosinophil quantification. Serum specific IgE levels at index hospitalization for all participants also were obtained. We defined higher severity in 2 ways: 1) requirement of intensive care therapy (ie, intensive care unit [ICU] admission, mechanical ventilation, and/or continuous positive pressure ventilation [CPAP]), and 2) longer hospital length of stay (LOS). Multivariable logistic regression was used to analyze the association between biomarkers and bronchiolitis severity, with the final model adjusted for demographics, clinical characteristics, and potential clustering by site. Among 880 infants in the analytical cohort, the median age was 3.0 months (interquartile range [IQR] 1.6-5.7 months), 60% were male, and 44% were non-Hispanic white. At hospitalization, 18% had blood eosinophil levels of ≥3%, and 20% had specific IgE of ≥ 0.35kU/L. With regard to outcomes, 15% received intensive care therapy, and 39% had increased hospital LOS. In multivariable models examining each biomarker in separate models, blood eosinophil level of ≥3% was not significantly associated with intensive care therapy (OR 0.89, 95% CI 0.50 - 1.56), nor hospital LOS (OR 0.78, 95% CI 0.58 - 1.06). By contrast, specific IgE had potential association with intensive care therapy (OR 1.35, 95% CI 0.87 - 2.11) but not hospital LOS. In a multivariable model for intensive care therapy, adjusted for both blood eosinophils and specific IgE, eosinophils remained non-significant while higher specific IgE was associated with higher risk (OR 1.53, 95% CI 0.99 - 2.37; p=0.05). In this multicenter study of infants hospitalized with bronchiolitis, we found that blood eosinophil level of ≥3% was not associated with the use of intensive care therapy and/or increased hospital LOS. By contrast, specific IgE had a borderline significant association with intensive care therapy, but not hospital LOS. Although neither biomarker is likely to provide helpful prognostic information, the specific IgE finding provides potential insight into the pathophysiology of more severe bronchiolitis. Further research is warranted into this mechanism, and other potential biomarkers for higher bronchiolitis severity.