Peripheral blood eosinophil count as a biomarker of exacerbation in stable chronic obstructive pulmonary disease outpatients: a prospective observational study

Background Peripheral blood eosinophil count is liable to many factors and has variability over time. There are few studies on the association between the rise of blood eosinophils and the exacerbation incidence in stable chronic obstructive pulmonary disease (COPD) patients. The association between the rise of blood eosinophils and the rate of exacerbation in stable COPD patients is controversial. Objective To study the relationship between the count of eosinophils in the peripheral blood and the incidence of COPD exacerbation in stable patients. Patients and methods This prospective inquiry was done on 46 patients diagnosed as suffering from stable COPD ‘on the report of the global initiative for chronic obstructive lung disease (GOLD) guidelines’ attending Ain Shams University hospital outpatient clinic. Results Forty-six stable COPD patients were classified into two groups (groups A and B) based on their median eosinophilic count of ‘250 cell/μl.’ Patients with high eosinophil count ‘group A’ (>250 cell/μl) had a significantly higher incidence of exacerbations (P=0.003), with a relative risk ratio of 2.77, as well as a higher number of exacerbations per patient (two exacerbations/patient) versus one exacerbation/three patients (P<0.001), and a shorter period to the first exacerbation (17 vs. 31 days) (P=0.024), compared with those with low eosinophil count ‘group B (≤250 cell/μl)’ during the study period. On the contrary, there was no significant difference between them in the incidence of pneumonia in relation to inhaled corticosteroid use. Conclusion The count of eosinophils in the peripheral blood is a reliable exacerbation biomarker in stable COPD patients.