Circulating eosinophil levels do not predict severe exacerbations in COPD: a retrospective study

Whether the level of circulating eosinophils in chronic obstructive pulmonary disease (COPD) patients can predict the risk of exacerbations of COPD (ECOPD) or response to treatment is debated. Here, we evaluate the prevalence of elevated eosinophils in COPD patients and its relationship with severe ECOPD requiring hospitalisation. We retrospectively reviewed the charts of COPD patients hospitalised in our centre between January 1, 2005 and November 30, 2015 because of ECOPD or other reasons (controls). In a second analysis, the ECOPD patients were divided into two subgroups based on having ECOPD in the next year after the index event or not. Circulating eosinophils, both during clinical stability and hospitalisation, as well as clinical and functional data and the relation to recurrent exacerbations were analysed. We studied 992 COPD patients (318 ECOPD patients and 674 controls). Among ECOPD patients, 121 had one or more ECOPD during the year after the index event. The prevalence of eosinophils ≥2% was 72% in ECOPD patients and 71% in controls (p=0.93). Among ECOPD patients, eosinophil levels ≥2%, ≥4% or ≥300 cells·μL(−1), either when clinically stable or during hospitalisation, did not show a significant association with the rate of recurrent severe exacerbations. The severity of airflow limitation was associated with recurrent exacerbations, but inhaled corticosteroid treatment was not. The majority of COPD patients have circulating eosinophils >2% and a significant association with the risk of severe ECOPD or response to inhaled corticosteroids was not demonstrated.