1. Department of Allergy and Clinical Immunology, Airway Sensation and Cough Research Laboratory, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
2. Department of Internal Medicine, Veterans Health Service Medical Center, Seoul, Korea.
3. Department of Internal Medicine, Gachon University Gil Medical Center, Incheon, Korea.
4. Department of Internal Medicine, Pusan National University School of Medicine, Pusan National University Hospital, Busan, Korea.
5. Department of Internal Medicine, Kangwon National University School of Medicine, Chuncheon, Korea.
6. Department of Internal Medicine, College of Medicine, Ewha Womans University, Seoul, Korea.
7. Department of Internal Medicine, Pusan National University Yangsan Hospital, Yangsan, Korea.
8. Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, Korea.
9. Department of Internal Medicine, Hanyang University Hospital, Seoul, Korea.
10. Department of Internal Medicine, Eulji Hospital, Eulji University School of Medicine, Seoul, Korea.
11. Division of Allergy, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
12. Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
13. Centre for Human & Applied Physiological Sciences, School of Basic & Medical Biosciences, Faculty of Life Sciences & Medicine, King's College London, London, UK.