1. Division of Allergy, Pulmonary and Critical Care Medicine, Department of Internal Medicine, Research Institute for Convergence of Biomedical Science and Technology, Pusan National University Yangsan Hospital, Yangsan, Republic of Korea.
2. Department of Internal Medicine, School of Medicine, Pusan National University, BusanRepublic of Korea.
3. Division of Pulmonary and Critical Care Medicine, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, SeoulRepublic of Korea.
4. Department of Pulmonary and Critical Care Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
5. Department of Statistics, Seoul National University, Seoul, Republic of Korea.