1. The Rheumatism Research Center, Catholic Research Institute of Medical Science, The Catholic University of Korea, Seoul 137-040, Korea.
2. Department of Internal Medicine, Inje University Ilsan Paik Hospital, Goyang 411-706, Korea.
3. Division of Rheumatology, Department of Internal Medicine, Seoul St. Mary's Hospital, The Catholic University of Korea, Seoul 137-040, Korea.