1. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
2. Department of Pulmonology, The Catholic University of Korea School of Medicine, Seoul, Korea.
3. Department of Internal Medicine, Konkuk University School of Medicine, Seoul, Korea.
4. Department of Internal Medicine, University of Dongguk College of Medicine, Dongguk University Ilsan Hospital, Goyang, Korea.
5. Department of Internal Medicine, Seoul Paik Hospital, Inje University College of Medicine, Seoul, Korea.
6. Department of Respiratory Medicine and Allergy, Soonchunhyang University School of Medicine, Seoul, Korea.
7. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea.
8. Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea.
9. Department of Pulmonary and Critical Care Medicine, Ajou University School of Medicine, Suwon, Korea.
10. Department of Internal Medicine, College of Medicine, Wonkwang University, Iksan, Korea.
11. Department of Internal Medicine, College of Medicine, Inha University, Incheon, Korea.
12. Department of Internal Medicine, Hallym University College of Medicine, Seoul, Korea.