The utility of using FeNO with blood eosinophil counts (BEC) in identifying inflammatory endotypes in stable state COPD.

<bold>Introduction:</bold> Eosinophilic airway inflammation is a treatable trait in airways disease. BEC is a known biomarker for treatment response in COPD but the role of FeNO is unclear. FeNO, at a cut off value of 20 ppb, may be helpful in identifying specific inflammatory endotypes to guide future treatment¹. <bold>Aims:</bold> As part of the BECCOPD study (IRAS 285200), this present analysis compared the relationship between FeNO, at a cut off value of 20 ppb, and BEC at the GOLD guideline blood eosinophil thresholds. <bold>Methods:</bold> Patients, stable on study entry, were recruited prospectively to the BECCOPD study from primary and secondary care. Participants with paired FeNO and BEC collected on study entry, were included in this analysis. <bold>Results:</bold> 295 participants were recruited to the study, 265 included in this analysis. Mean (SD) age 71 (7), mean FEV1% predicted 55 (23). 47% female, median eMRCD 3 (3-4),69% ex-smokers,70% receiving inhaled corticosteroids. Participants were sub-divided into different FeNO and BEC groups shown below. <table-wrap><object-id>erj;64/suppl_68/PA3981/T1</object-id><object-id>T1</object-id><object-id>t1</object-id><table><colgroup><col></col><col></col><col></col><col></col></colgroup><tbody><tr><td></td><td>BEC <0.1</td><td>BEC 0.1- 0.29</td><td>BEC ≥ 0.3</td></tr><tr><td>FeNO <20</td><td> 31</td><td> 117</td><td> 36</td></tr><tr><td>FeNO ≥20</td><td> 12</td><td> 47</td><td> 22</td></tr></tbody></table></table-wrap> Overall, intraclass correlation coefficient between FeNO and BEC was less than 0.1 indicating poor reliability. <bold>Conclusion:</bold> Discordance was observed between FeNO and BEC across all treatment thresholds. This effect was more in smokers at the 0.1 threshold. Higher exacerbation frequency was seen in discordant groups showing a potential role of FeNO to guide treatment particularly at the 0.1 threshold. <bold>Acknowledgements:</bold> The BECCOPD study is funded by GSK(214233) via the supported studies program. <bold>References:</bold> 1. Alcazar-Navarrete et al. European Respiratory Journal Jan 2018,51(1)1701457.