1. Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Internal Medicine, Hallym University Kangnam Sacred Heart Hospital, Hallym University College of Medicine, Seoul, Korea.
2. Deparment of Internal Medicine, Dongguk University Gyeongju Hospital, Dongguk Univiersity College of Medicine, Gyeongju, Korea.
3. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Chungbuk National University Hospital, Chungbuk National University College of Medicine, Cheongju, Korea.
4. Department of Statistics and Actuarial Science, Soongsil University, Seoul, Korea.
5. Department of Biostatistics, College of Medicine, The Catholic University of Korea, Seoul, Korea.
6. Division of Pulmonary Medicine and Allergy, Department of Internal Medicine, Hanyang University College of Medicine, Seoul, Korea.
7. Department of Family Medicine/Supportive Care Center, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
8. Department of Clinical Research Design & Evaluation, Samsung Advanced Institute for Health Science & Technology (SAIHST), Sungkyunkwan University, Seoul, Korea.