BACKGROUND: The 2018 Global Initiative for Chronic Obstructive Lung Disease Report reveals that the blood eosinophil count could forecast the risk of flare-ups. This study explored the correlations of blood eosinophils with fractional exhaled nitric oxide (FeNO) and pulmonary function parameters in acute exacerbation of chronic obstructive pulmonary disease (AECOPD).

MATERIAL AND METHODS: The data of patients with AECOPD at our hospital admitted between July 2018 and June 2019 were retrospectively analyzed. All patients were stratified into an eosinophilic group (≥2%) or a noneosinophilic group (<2%) based on the peripheral eosinophil count per centum. Cross-sectional analysis was performed to compare clinical characteristics, percentage of eosinophils, FeNO, and pulmonary function between the 2 groups.

RESULTS: After applying the inclusion/exclusion criteria, 247 patients were included. FeNO values were higher in eosinophilic group (n=97) than in noneosinophilic group (n=150) (P=0.005). The forced expiratory volume in 1 second% predicted (FEV1% predicted), FEV1, and forced vital capacity (FVC) were higher in the eosinophilic group than in the noneosinophilic group (P=0.043; P=0.040; and P=0.011, respectively). Blood eosinophilia showed positive correlations with FeNO (P=0.004) and spirometry variables (FEV₁ [% predicted], P=0.003; FEV₁, P<0.001; and FVC, P<0.001). An FeNO level of 22.5 ppb was the best cutoff value to predict blood eosinophilia (P=0.000).

CONCLUSIONS: Blood eosinophil count is a likely biomarker that can predict positive relationship with FeNO values and pulmonary function parameters.

Keywords: Eosinophils, Nitric Oxide, Pulmonary Disease, Chronic Obstructive, Respiratory Function Tests, Aged, 80 and over, Breath Tests, Cross-Sectional Studies, Eosinophilia, Exhalation, Leukocyte Count, Symptom Flare Up