1. Department of Internal Medicine, Ewha Womans University College of Medicine, Seoul, Korea
2. Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea
3. Department of Internal Medicine, Korea University College of Medicine, Seoul, Korea
4. Department of Internal Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea
5. Department of Internal Medicine, Soonchunhyang University College of Medicine, Cheonan, Korea
6. Department of Internal Medicine, Hallym University College of Medicine, Chuncheon, Korea
7. Department of Biostatistics, Korea University College of Medicine, Seoul, Korea