1. Division of Pulmonology and Allergy, Department of Internal Medicine, Seoul St. Mary's Hospital, College of Medicine, The Catholic University School of Medicine, Seoul, Korea.
2. Division of Allergy and Pulmonology, Department of Internal Medicine, Bucheon St. Mary's Hospital, The Catholic University School of Medicine, Bucheon, Korea.
3. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Ulsan University Hospital, Ulsan University College of Medicine, Ulsan, Korea.
4. Department of Pulmonary and Critical Care Medicine, Chungnam National University Hospital, Daejeon, Korea.