Blood eosinophils and lung function loss: from passive prediction to active prevention?

The blood eosinophil count has more than lived up to its potential as a prognostic and predictive biomarker in the 10 years since it earned the accolade of being biomarker of the year [1]. It is now clear that in patients already diagnosed with asthma and COPD, the blood eosinophil count predicts exacerbation frequency [2, 3], response to inhaled corticosteroids (ICS) [4, 5], the acute response to systemic corticosteroids [6], and response to monoclonal antibody therapy targeting type-2 cytokines [7, 8]. Management guided by blood eosinophil count is now the standard of care in COPD and severe asthma.