Clinical implications of blood eosinophil count in patients with non-asthma–COPD overlap syndrome COPD

Jin Hwa Song,1 Chang-Hoon Lee,1 Jin Woo Kim,2 Won-Yeon Lee,3 Ji Ye Jung,4 Joo Hun Park,5 Ki Suck Jung,6 Kwang Ha Yoo,7 Yong Bum Park,8 Deog Keom Kim9 1Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University Hospital, 2Division of Pulmonology, Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, 3Department of Internal Medicine, Yonsei University Wonju College of Medicine, Wonju, Gangwon-do, 4Division of Pulmonology, Department of Internal Medicine, Severance Hospital, Yonsei University College of Medicine, Seoul, 5Department of Pulmonary and Critical Care Medicine, Ajou University School of Medicine, Suwon, 6Division of Pulmonary Medicine, Department of Internal Medicine, Hallym University Sacred Heart Hospital, Hallym University Medical School, Anyang, Gyeonggi-do, 7Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Konkuk University Medical Center, Konkuk University School of Medicine, 8Division of Pulmonary, Allergy and Critical Care Medicine, Department of Internal Medicine, Kangdong Sacred Heart Hospital, 9Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul Metropolitan Government-Seoul National University Boramae Medical Center, Seoul National University College of Medicine, Seoul, Republic of Korea Background: Recent studies that assessed the relevance of the blood eosinophil count as a biomarker in patients with COPD may have overestimated it because they included patients with asthma–COPD overlap syndrome (ACOS). We investigated the clinical implications of the blood eosinophil count in patients with non-ACOS COPD.Patients and methods: From a Korean COPD Subtype Study (KOCOSS) cohort, we selected patients with non-ACOS COPD after excluding ACOS patients according to Spanish criteria. Clinical characteristics and the incidence of moderate-to-severe exacerbation were compared among the four groups stratified according to the quartiles of blood eosinophil percent and count.Results: Of the KOCOSS cohort of 1,132 patients with COPD, 467 non-ACOS COPD patients (41.2%) with data of blood eosinophil count remained after excluding those with ACOS based on the Spanish definition. There was no difference in clinical characteristics among groups classified according to the quartiles of eosinophil percent and count. On multivariate logistic regression, eosinophil quartiles in percent and absolute count were not associated with the incidence of moderate-to-severe acute exacerbations of COPD (AECOPD). The eosinophil count did not affect the risk of AECOPD or forced expiratory volume in 1second (FEV1) changes according to exposure to inhaled corticosteroid (ICS). However, by increasing the cutoff value for the eosinophil count from 200/µL to 600/µL, the odds ratio for risk of exacerbation increased serially from 0.82 to 2.96 on trend analysis.Conclusion: In patients with non-ACOS COPD, the blood eosinophil count and percent were not associated with FEV1 changes, quality of life (QoL), AECOPD frequency, or response to ICS. The clinical implication of the blood eosinophil count should not be overestimated in patients with non-ACOS COPD. Keywords: eosinophil, chronic obstructive lung disease, asthma, acute exacerbation, inhaled corticosteroid