Sputum eosinophils and high serum IgE are independently associated with overuse of rescue bronchodilators in asthmatics

Overuse of rescue bronchodilators in asthma is associated with increased morbidity and mortality. The relationship between T2 biomarkers and overuse of rescue bronchodilators has not been investigated so far. Here we conducted a large retrospective cross-sectional study leveraging our asthma clinic data base to evaluate the relationship between the item 6 of the asthma control questionnaire (ACQ) and the levels of blood and sputum eosinophils, FeNO and total serum IgE in 2167 asthmatics the majority of whom (73%) were receiving maintenance with ICS/LABA leaving a minority of patients treated with SABA or SABA/SAMA only. Overuse of rescue was defined as a score ≥ 3 at the item 6 of ACQ. Analyses were performed by univariate and multivariate logistic regression after stratification of T2 biomarkers following clinically pertinent thresholds. There were significant correlations between all T2 biomarkers ( p < 0.0001), the strongest correlation being observed between blood and sputum eosinophils (Rs = 0,52) and the weakest between IgE and FeNO (Rs = 0,23). After univariate analysis, all T2 biomarkers associated with overuse of rescue bronchodilators and this persisted after adjustment for age, BMI, smoking and FEV 1 % predicted. However, this only held true for the highest threshold for FeNO (50 ppb) and IgE (700 KU/L) while sputum eosinophils and blood eosinophils displayed a significant association over thresholds ranging from 1% to 50% and from 150 to 500/µl respectively. After multiple logistic regression analysis including the four T2 biomarkers, only sputum eosinophils and high IgE level maintained their association with the overuser status. Sputum eosinophils and high serum IgE emerge as T2 biomarker independently associated with overuse of rescue bronchodilators in asthmatics.