1. Department of Internal Medicine, Hanyang University Guri Hospital, Guri, Korea.
2. Department of Internal Medicine, Sungkyunkwan University School of Medicine, Seoul, Korea.
3. Department of Internal Medicine, University of Ulsan College of Medicine, Seoul, Korea.
4. Department of Internal Medicine, Ewha Womans University School of Medicine, Seoul, Korea.
5. Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea.
6. Department of Internal Medicine, Hallym University Medical Center, Anyang, Korea.
7. Department of Internal Medicine, Soonchunhyang University College of Medicine, Cheonan, Korea.
8. Department of Internal Medicine, The Catholic University of Korea Incheon St. Mary's Hospital, Incheon, Korea.
9. Department of Internal Medicine, Ajou University School of Medinie, Suwon, Korea.
10. Department of Internal Medicine, Korea University College of Medicine, Seoul, Korea.
11. Department of Internal Medicine, Yonsei University College of Medicine, Wonju, Korea.
12. Department of Biostatistics and Bioinformatics, Duke University, Durham, NC, USA.