1. Division of Pulmonology and Allergy, Department of Internal Medicine, Veterans Health Service Medical Center, Seoul, Korea.
2. Department of Allergy and Clinical Immunology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
3. Department of Internal Medicine, Hospital Medicine Center, Seoul National University Hospital, Seoul, Korea.
4. Department of Internal Medicine, Kyung Hee University Medical Center, Seoul, Korea.
5. Department of Internal Medicine, Dankook University Hospital, Cheonan, Korea.
6. Division of Pulmonology, Allergy and Critical Care Medicine, Department of Internal Medicine, Korea University College of Medicine, Seoul, Korea.
7. Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
8. Institute of Allergy and Clinical Immunology, Seoul National University Medical Research Center, Seoul, Korea.
9. Upper Airways Research Laboratory, Department of Otorhinolaryngology, Ghent University, Ghent, Belgium.