1. Department of Pulmonary and Critical Care Medicine, Ajou University School of Medicine, Suwon, Korea.
2. Department of Pulmonary and Critical Care Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
3. Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, Korea.
4. Department of Internal Medicine, Seoul Metropolitan Government-Seoul National University Boramae Medical Center, Seoul, Korea.
5. Department of Internal Medicine, Kyung Hee University Hospital, Seoul, Korea.
6. Department of Internal Medicine, CHA Bundang Medical Center, CHA University, Seongnam, Korea.
7. Department of Internal Medicine, Hallym University Sacred Heart Hospital, Seoul, Korea.
8. Department of Internal Medicine, Hallym University Sacred Heart Hospital, Anyang, Korea.
9. Department of Internal Medicine, Samsung Medical Center, Seoul, Korea.
10. Department of Internal Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
11. Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea.
12. Department of Internal Medicine, Wonkwang University Sanbon Hospital, Gunpo, Korea.
13. Department of Internal Medicine, St. Mary's Hospital, Seoul, Korea.
14. Department of Internal Medicine, Yeouido St. Marry's Hosital, The Catholic University of Korea College of Medicine, Seoul, Korea.
15. Department of Internal Medicine, Uijeongbu St. Marry's Hospital, Uijeongbu, Korea.
16. Department of Internal Medicine, Konkuk University College of Medicine, Seoul, Korea.