Biomarker-based detection of asthma–COPD overlap syndrome in COPD populations

Asthma-chronic obstructive pulmonary disease (COPD) overlap syndrome (ACOS) was proposed by the science committees of both Global Initiative for Asthma (GINA) and Global Initiative for Chronic Obstructive Lung Disease (GOLD). However, the definition of ACOS has remained unclear all over the world, and the prevalence rate of ACOS is basically dependent on the patient's symptoms or the physician's opinion, based on questionnaire testing. In the current case report, we investigated the prevalence rate of COPD patients with high levels of fractional exhaled nitric oxide (FENO) or immunoglobulin E (IgE) as candidate markers of ACOS in COPD, as a multicenter, cross-sectional study. Outpatients with COPD were enrolled from Tohoku University Hospital, Sendai, Japan, and five hospitals (Tohoku University Hospital, Sendai, Japan; NTT East Tohoku Hospital, Sendai, Japan; Wakayama Medical University Hospital, Kimiidera, Japan; Hiraka General Hospital, Yokote, Japan; Iwate Prefectural Isawa Hospital, Oshu, Japan) with pulmonary physicians from March 1, 2013 to February 28, 2014. When they were estimated using 35 ppb as the cutoff value of FENO, the prevalence rate of ACOS was 16.3% in COPD. When estimated by both FENO and IgE, the high-FENO/high-IgE group was 7.8% in COPD. To the best of our knowledge, this study is the first to detect the prevalence rate of ACOS in COPD populations by using objective biomarkers. The results from the current study should be useful to identify the subgroup requiring early intervention by inhaled corticosteroids/long-acting beta agonist combination in COPD in order to improve the long-term management for ACOS.