Blood eosinophils, specific immunoglobulin E, and bronchiolitis severity

Bronchiolitis is the leading cause of hospitalization for United States infants. Blood eosinophil and serum specific IgE (sIgE) levels are separately linked to clinical severity but few studies have examined these biomarkers together.

Among infants hospitalized for bronchiolitis, we investigated the association between (1) blood eosinophilia and severity, (2) sIgE sensitization and severity, and (3) interaction between the two biomarkers on severity.

We enrolled 1016 infants hospitalized for bronchiolitis between 2011 and 2014 across 17 U.S. hospitals into a prospective cohort study. Of those, 873 (86%) had eosinophils measured and all had sIgE levels from blood collected at hospitalization. We investigated higher bronchiolitis severity using intensive care therapy as the outcome (i.e., intensive care unit admission, intubation, and/or receipt of continuous positive pressure ventilation).

Among 873 infants in the analytic cohort, 18% had blood eosinophilia of ≥3%, and 20% were positive for sIgE. With regard to bronchiolitis severity, 15% received intensive care therapy. In unadjusted analyses, eosinophils ≥3% was not associated with intensive care therapy, while sIgE was associated with a significantly higher risk (odds ratio [OR]: 1.44, 95% confidence interval [CI]: 1.08-1.92; p = .01). In a multivariable model for intensive care therapy, eosinophilia remained unassociated with severity, and sIgE remained associated (OR: 1.60, 95% CI: 1.05-2.45; p = .03). Also, sIgE did not modify the association between eosinophil level and intensive care therapy (p_interaction  = .14).

Blood eosinophilia of ≥3% was not associated with bronchiolitis severity. By contrast, sIgE was independently associated with bronchiolitis severity and did not modify the association between eosinophil level and severity.