1. Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
2. Department of Internal Medicine, School of Medicine, Ewha Womans University, Seoul, Korea.
3. Department of Internal Medicine, Seoul Metropolitan Government-Seoul National University Boramae Medical Center, Seoul, Korea.
4. Department of Internal Medicine, School of Medicine, Kyungpook National University, Daegu, Korea.
5. Department of Internal Medicine, College of Medicine, Yonsei University, Seoul, Korea.