Clinical characteristics and exacerbation risk of chronic obstructive pulmonary disease patients with persistent type 2 inflammation on inhaled corticosteroid

<bold>Background:</bold> The role of type 2 biomarker fractional exhaled nitric oxide (FeNO) in COPD remains controversial. While inhaled corticosteroid (ICS) can suppress FeNO, no studies have targeted patients with persistently elevated FeNO on ICS. <bold>Aims:</bold> To investigate the clinical characteristics and exacerbation risk of COPD patients on ICS with high FeNO. <bold>Methods:</bold> A retrospective study was conducted in COPD patients on ICS who had FeNO test from January 2016 to December 2023 in Princess Margaret Hospital. Patients with previous physician-diagnosed asthma were excluded. The clinical characteristics of high (≥20ppb) and low FeNO (<20ppb) patients were compared by Chi-square and T-test. Association between COPD exacerbations in the past 12 months and FeNO was assessed by logistic regression. <bold>Results:</bold> 107 COPD patients on ICS performed FeNO test during the study period. 41 (38%) of them had high FeNO and 66 (62%) had low FeNO. High FeNO group had significantly higher blood eosinophil (470 cells/μL vs. 230 cells/μL, p = 0.028) and more exacerbations in previous 12 months (2.1 vs. 0.7, p = 0.007). On simple logistic regression, high FeNO and post-bronchodilator FEV1 had significant association with exacerbation, with OR 2.26 (p = 0.045) and 0.98 (p = 0.031) respectively. Adjusted OR for high FeNO was 2.48 (p = 0.037) on multiple logistic regression. Combining high FeNO and blood eosinophil further increased adjusted OR to 4.02 (p=0.022). <bold>Conclusion:</bold> COPD patients on ICS with elevated FeNO, especially with high blood eosinophil, had increased risk of exacerbations. Prospective study is required to further investigate the association.