1. Division of Pulmonary and Critical Care Medicine, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
2. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Inha University Hospital, Inha University School of Medicine, Incheon, Korea.
3. Division of Pulmonary Medicine, Department of Internal Medicine, Gachon Medical School Gil Medical Center, Incheon, Korea.
4. Department of Internal Medicine, Kyungpook National University Hospital, Daegu, Korea.
5. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University College of Medicine, and Lung Institute, Seoul National University Hospital, Seoul, Korea.
6. Division of Respiration and Allergy Medicine, Soonchunhyang University Hospital, Seoul, Korea.
7. Department of Internal Medicine, Bucheon Hospital, Soonchunhyang University School of Medicine, Bucheon, Korea.
8. Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea.
9. Department of Internal Medicine, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, Korea.
10. Department of Pulmonary and Critical Care Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
11. Department of Internal Medicine, Seoul Paik Hospital, Inje University, Seoul, Korea.
12. Department of Internal Medicine, Hallym University College of Medicine, Kangdong Sacred Heart Hospital, Seoul, Korea.