Didier Cataldo,1 Jean-Louis Corhay,1 Eric Derom,2 Renaud Louis,1 Eric Marchand,3,4 Alain Michils,5 Vincent Ninane,6 Rudi Peché,7 Charles Pilette,8 Walter Vincken,9 Wim Janssens10 1Department of Respiratory Diseases, CHU Liège, University of Liège, Liège, 2Department of Respiratory Medicine, Ghent University Hospital, Ghent, 3Department of Respiratory Medicine, CHU – UCL – Namur, Université catholique de Louvain, Yvoir, 4Molecular Physiology Research Unit (URPhyM)-NARILIS, Laboratory of General Physiology, University of Namur, Namur, 5Chest Department, Erasme University Hospital, Université Libre de Bruxelles, Brussels, 6Department of Respiratory Medicine, University Hospital Saint-Pierre, Université Libre de Bruxelles, Brussels, 7Department of Respiratory Medicine, University Hospital Vésale, Montigny-le-Tilleul, 8Department of Respiratory Medicine, Cliniques universitaires St Luc, Université Catholique de Louvain, Brussels, 9Respiratory Division, University Hospital Brussels (UZ Brussel), Vrije Universiteit Brussel, Brussels, 10Department of Respiratory Diseases, University Hospitals Leuven, Leuven, Belgium Introduction: Patients with chronic airway disease may present features of both asthma and COPD, commonly referred to as asthma–COPD overlap syndrome (ACOS). Recommendations on their diagnosis are diffuse and inconsistent. This survey aimed to identify consensus on criteria for diagnosing ACOS.Methods: A Belgian expert panel developed a survey on ACOS diagnosis, which was completed by 87 pulmonologists. Answers chosen by ≥70% of survey respondents were considered as useful criteria for ACOS diagnosis. The two most frequently selected answers were considered as major criteria, others as minor criteria. The expert panel proposed a minimal requirement of two major criteria and one minor criterion for ACOS diagnosis. Respondents were also asked which criteria are important for considering inhaled corticosteroids prescription in a COPD patient.Results: To diagnose ACOS in COPD patients, major criteria were “high ...