Systemic and airway eosinophilia are recognised features of asthma. There are, however, patients who exhibit discordance between local and systemic eosinophilia. In this study, we sought to determine the prevalence and characteristics of patients with concordant and discordant systemic and bronchial eosinophilia. We conducted a retrospective study on 508 asthmatics with successful sputum induction. We assessed the relationship between blood and sputum eosinophils by breaking down the population into four groups according to blood (≥400 cells per mm3) and sputum (≥3%) eosinophils. Then, we prospectively reassessed the link between eosinophils and asthma control (Asthma Control Questionnaire (ACQ)) and exacerbation rate in a new cohort of 250 matched asthmatics. In our retrospective cohort, asthmatics without eosinophilic inflammation were the largest group (49%). The group with isolated sputum eosinophilia (25%) was, compared with noneosinophilic asthma, associated with lower forced expiratory volume in 1 s (FEV1) and FEV1/forced vital capacity ratio and higher bronchial hyperresponsiveness and exhaled nitric oxide fraction (FeNO). Asthmatics exhibiting isolated systemic eosinophilia (7%) had similar characteristics as noneosinophilic asthmatics. The group with concordant systemic and airway eosinophilia (19%) showed remarkable male predominance, and had the lowest airway calibre, asthma control and quality of life, and the highest bronchial hyperresponsiveness, FeNO and exacerbation rate. The prospective cohort confirmed the different subgroup proportions and the higher ACQ and exacerbation rates in cases of diffuse eosinophilia compared with noneosinophilic asthmatics. Concomitant systemic and bronchial eosinophilic inflammation contribute to poor asthma control.
Schleich et al. (2014) studied this question.