Association of Submucosal Eosinophilia With Blood and Bronchoalveolar Lavage Eosinophilia in Adults With Severe Refractory Asthma

Abstract

Abstract Objectives Asthma is a chronic inflammatory disease of the lungs, and for individuals with persistently uncontrolled symptoms despite maximal medical therapy, an endobronchial biopsy and bronchoalveolar lavage (BAL) may be obtained to guide therapy. Given the invasive nature of this procedure, most patients obtain blood eosinophil counts. The goal of this study was to compare blood, BAL, and biopsy eosinophils to identify whether there is a correlation between these various approaches. Methods A retrospective study was conducted in adult patients (n = 220) who had been seen in the Refractory Obstructive Lung Disease clinic over a 10-year period (2008-2017). All the patients had been clinically diagnosed with severe refractory asthma. Clinical data were obtained through review of the electronic medical records. Results Patients with submucosal eosinophilia had a greater prevalence of intraepithelial eosinophils (50.9% vs 2.3%, P < .001), intraepithelial neutrophils (36.7% vs 9.3%, P < .001), and intraepithelial lymphocytes (52.5% vs 18.6%, P < .001). In contrast, no significant differences were noted between the samples with submucosal eosinophilia present versus submucosal eosinophilia absent for polymorphonuclear leukocyte (PMN) percent, lymphocyte percent, or macrophage percent in BAL. There was a significant difference in eosinophil percentage between the two groups (8.7% vs 1.1%, P = .004). When submucosal eosinophilia was divided into mild (1-10 eosinophils/HPF), moderate (11-20 eosinophils/HPF), and severe (>20 eosinophils/HPF), mean eosinophilia trended more with eosinophilia in the BAL than with the peripheral blood. There was poor correlation (r = 0.31, P = .0001) between eosinophil levels in the blood and BAL. Conclusion Compared to BAL, histopathologic data may more accurately characterize the underlying pathophysiology in severe asthmatics by providing a more detailed quantification of the airway inflammatory infiltrates. Moreover, blood eosinophilia may not be as representative of airway inflammation in patients with severe refractory asthma given the poor correlation between eosinophil levels in the blood and BAL.