1. Department of Pulmonary and Critical Care Medicine, Wonkwang University Sanbon Hospital, Gunpo, Korea.
2. Department of Allergy and Clinical Immunology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
3. Asthma Center, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
4. Clinical Research Center for Chronic Obstructive Airway Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
5. Department of Pulmonary and Critical Care Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.