1. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Konkuk University School of Medicine, Chungju, Korea.
2. Department of Internal Medicine, Konkuk University Chungju Hospital, Konkuk University School of Medicine, Chungju, Korea.
3. Department of Laboratory Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
4. Division of Pulmonary and Critical Care Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.