In an era of
precision medicine, it seems regressive that we do not use stratified approaches to direct treatment of oral
corticosteroids during an exacerbation of
chronic obstructive pulmonary disease (
COPD). This is despite evidence suggesting that 40% of
COPD patients have eosinophilic
inflammation and this is an
indicator of
corticosteroid response. Treatments with oral
corticosteroids are not always effective and not without harm, with significant and increased risk of
hyperglycemia,
sepsis, and fractures. Eosinophils are innate immune cells with an incompletely understood role in the pathology of airway disease. They are detected at increased levels in some patients and can be measured using non-invasive methods during states of exacerbation and stable periods. Despite the eosinophil having an unknown mechanism in
COPD, it has been shown to be a marker of
length of stay in severe hospitalized exacerbations, a predictor of risk of future exacerbation and exacerbation type. Although limited, promising data has come from one prospective clinical trial investigating the eosinophil as a
biomarker to direct systemic
corticosteroid treatment. This identified that there were statistically significant and clinically worsened symptoms in patients with low eosinophil levels who were prescribed
prednisolone, demonstrating the potential utility of the eosinophil. In an era of
precision medicine our patients' needs are best served by accurate diagnosis, correct identification of maximal treatment response and the abolition of harm. The peripheral blood eosinophil count could be used towards reaching these aims.