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