1. Department of Internal Medicine, Pusan National University Yangsan Hospital, Yangsan, Korea.
2. Department of Chest Medicine, Masan National Tuberculosis Hospital, Masan, Korea.
3. Department of Internal Medicine, Chonnam National University Hospital, Gwangju, Korea.
4. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
5. Department of Pulmonary and Critical Care Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.