The Value of <scp>FeNO</scp> and Peripheral Blood Eosinophils in Assessing Airway Eosinophilic Inflammation in Patients With Acute Exacerbations of Chronic Obstructive Pulmonary Disease

ABSTRACT Background To evaluate the clinical value of fractional exhaled nitric oxide (FeNO) levels and peripheral blood eosinophil (EOS) counts and percentages in assessing airway eosinophilic inflammation in patients with acute exacerbations of chronic obstructive pulmonary disease (AECOPD). Methods In total, 119 AECOPD patients were included in the study. Patients were divided based on the percentage of EOS in their sputum into the airway EOS inflammation group (29 patients) and the non‐airway EOS inflammation group (90 patients). The diagnostic values of FeNO and peripheral blood EOS for detecting airway EOS inflammation in AECOPD patients were assessed. Results The airway EOS inflammation group had higher peripheral blood EOS counts and percentages. FeNO, peripheral blood EOS counts and percentages were significantly correlated with sputum EOS percentages. ROC curve analysis showed that the optimal cut‐off values for predicting airway EOS inflammation were 18.5 ppb for FeNO, with sensitivities and specificities of 76% and 61%, respectively; 0.335 × 10 9 /L for peripheral blood EOS count, with sensitivities and specificities of 41% and 98%, respectively; and 3.56% for peripheral blood EOS percentage, with sensitivities and specificities of 59% and 86%, respectively. Conclusions FeNO, peripheral blood EOS counts and percentages have a strong correlation with airway EOS inflammation. The levels of FeNO and peripheral blood EOS counts and percentages can effectively predict airway EOS inflammation in AECOPD patients.