1. Respiratory Division, Department of Internal Medicine, Soonchunhyang University Gumi Hospital, Soonchunhyang University School of Medicine, Gumi, Korea.
2. Department of Internal Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea.
3. Respiratory Division, Department of Internal Medicine, Soonchunhyang University Seoul Hospital, Soonchunhyang University School of Medicine, Seoul, Korea.
4. Department of Internal Medicine, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea.
5. Department of Internal Medicine, Jeonbuk National University Medical School, Jeonju, Korea.