1. Department of Internal Medicine, Konkuk University School of Medicine, Seoul, Korea.
2. Department of Internal Medicine, Hallym Univesity College of Medicine, Hallym Univesity Kangnam Sacred Heart Hospital, Seoul, Korea.
3. Department of Internal Medicine, Korea University College of Medicine, Korea University Guro Hospital, Seoul, Korea.
4. Department of Internal Medicine, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam, Korea.
5. Department of Internal Medicine, Gachon University Graduate School of Medicine, Gachon University Gil Medical Center, Incheon, Korea.
6. Department of Internal Medicine, Inha University School of Medicine, Inha University Hospital, Incheon, Korea.
7. Department of Internal Medicine, Soonchunhyang University College of Medicine, Soonchunhyang University Cheonan Hospital, Cheonan, Korea.
8. Department of Internal Medicine, Korea University College of Medicine, Korea University Anam Hospital, Seoul, Korea.
9. Department of Internal Medicine, Soonchunhyang University College of Medicine, Soonchunhyang University Bucheon Hospital, Bucheon, Korea.
10. Department of Internal Medicine, Hanyang University College of Medicine, Hanyang University Guri Hospital, Guri, Korea.
11. Department of Internal Medicine, Korea University College of Medicine, Korea University Ansan Hospital, Ansan, Korea.
12. Department of Internal Medicine, The Catholic University of Korea School of Medicine, The Catholic University of Korea St. Mary's Hosptial, Seoul, Korea.
13. Department of Internal Medicine, Kyungpook National University College of Medicine, Kyungpook National University Hospital, Daegu, Korea.
14. Department of Internal Medicine, Ajou University School of Medicine, Ajou University Hospital, Suwon, Korea.
15. Department of Internal Medicine, Wonkwang University School of Medicine, Wonkwang University Hospital, Iksan, Korea.
16. Department of Internal Medicine, Yeungnam University College of Medicine, Yeungnam University Medical Center, Daegu, Korea.
17. Department of Internal Medicine, Yonsei University Wonju College of Medicine, Yonsei University Wonju Christian Hospital, Wonju, Korea.
18. Department of Biostatistics, Korea University College of Medicine, Seoul, Korea.