1. Department of Internal Medicine, Division of Rheumatology, Hanyang University College of Medicine and the Hospital for Rheumatic Diseases, Seoul, Korea; Hospital for Rheumatic Diseases, Hanyang University Medical Center, Seoul 133-792, Korea
2. Department of Internal Medicine, Chosun University College of Medicine, Kwangju, Korea
3. Department of Internal Medicine, Eulji University School of Medicine, Daejeon, Korea
4. Department of Preventive Medicine, Hanyang University College of Medicine, Seoul, Korea