1. Department of Internal Medicine, Chonnam National University Hospital, Gwangju, Korea.
2. Department of Pulmonary and Critical Care Medicine, Kyung Hee University Hospital at Gangdong, School of Medicine, Kyung Hee University, Seoul, Korea.
3. Division of Pulmonary and Critical Care Medicine, Department of Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
4. Division of Pulmonary and Critical Care Medicine, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
5. Division of Pulmonology, Samsung Changwon Hospital, Changwon, Korea.
6. Division of Pulmonary and Critical Care Medicine, Department of Medicine, Ewha Medical Center and Ewha Medical Research Institute, Ewha Womans University School of Medicine, Mokdong Hospital, Seoul, Korea.
7. Department of Internal Medicine, Chung-Ang University School of Medicine, Seoul, Korea.
8. Department of Internal Medicine, College of Medicine, Gyeongsang Institute of Health Sciences, Gyeongsang National University, Jinju, Korea.