Study Investigates Blood Eosinophil Count as Prognostic Biomarker for COPD

Inhaled corticosteroids, used for preventing acute exacerbation of chronic obstructive pulmonary disease (COPD), often lead to increased high blood eosinophil count, while low blood eosinophil count is often associated with pneumonia risk—however, the prognostic role of blood eosinophil count has not yet been explored. In a recent study, researchers found that the severity of emphysema was independently linked with low blood eosinophil count and the longer survival period was associated with increased blood eosinophil count.

The researchers recruited patients with COPD from 16 hospitals of the Korean Obstructive Lung Disease cohort and the COPD in Dusty Area cohort of Kangwon University Hospital. Patients from the 2 cohorts were combined and then divided based on their blood eosinophil count into 3 groups—high (≥5%), middle (2%—5%), and low (<2%). Demographic data was collected from the patients, as well as data from the St George Respiratory Questionnaire, a 6-minute walk test, and spirometry.

“Recently, high blood eosinophil count has been recognized as a biomarker for predicting the response to inhaled corticosteroids in prevention of acute exacerbation, and low blood eosinophil count is associated with the risk of pneumonia in COPD patients taking inhaled corticosteroids,” noted the authors. “However, there is no consensus regarding what criteria of blood eosinophil count should be used for assessing the therapeutic efficacy.”

Following an analysis of the data, the results suggested that the high group had longer 6-minute walk distance, higher body mass index, lower emphysema index, and higher inspiratory capacity/total lung capacity ratio. Furthermore, the survival period increased with increasing blood eosinophil count. However, the multivariate linear regression analysis demonstrated that the emphysema index was independently and negatively correlated with blood eosinophil count, according to the study.

“The beneficial role of inhaled corticosteroids in the high eosinophil group appears to be partly explained by our finding that this group has fewer emphysematous features that would respond well to pharmacological intervention,” the researchers explained. “Previous studies have reported that, in the high eosinophil group of COPD, acute exacerbation is better prevented or treated using inhaled corticosteroids.”

The authors concluded that although the severity of emphysema was independently associated with low blood eosinophil count, while longer survival periods were linked with a higher count, this result was not proven in the multivariate analysis.

Reference

Oh YM, Lee KS, Hwang SC, et al. Blood eosinophil count as a prognostic biomarker in COPD. [published online October 31, 2018]. Int J Chron Obstruct Pulmon Dis. doi.org: 10.2147/COPD.S179734.