1. Department of Biomedical Informatics, Asan Medical Center, Seoul, Korea.
2. Department of Pulmonary and Critical Care Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
3. Department of Emergency Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
4. Division of General Internal Medicine, Brigham and Women's Hospital, Boston, MA, USA.