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High Diagnostic Value of Anticalpastatin Autoantibodies in Rheumatoid Arthritis Detected by ELISA Using Human Erythrocyte Calpastatin as Antigen
SACHIKO IWAKI-EGAWA, HIROAKI MATSUNO, KAZUO YUDOH, FUJIO NAKAZAWA, KYOUSUKE MIYAZAKI, AKIRA OCHIAI, SHUNSEI HIROHATA, MASATOSHI SHIMIZU, and YASUHIRO WATANABE
ABSTRACT.
Methods. We performed a highly sensitive ELISA for IgG and IgM anticalpastatin autoantibodies in human sera using human erythrocyte calpastatin as an antigen. Samples were diluted 1:2000 for the measurement of IgG and 1:400 for IgM. Results. IgG anticalpastatin antibodies were found in the sera of 48 of 58 patients (82.8%) with RA. In contrast, IgG anticalpastatin antibodies were found in the sera of only 2 of 11 (8.3%) patients with osteoarthritis (OA). Compared to sera from patients with other autoimmune diseases, anticalpastatin antibody sensitivity for RA was better than that of systemic lupus erythematosus (5.6%), systemic sclerosis (0%), mixed connective tissue disease (0%), and Sjögren's syndrome (20%). IgG anticalpastatin antibodies also showed high specificity (96.1%) for RA. Almost 90% of patients with RA were positive for IgG or IgM anticalpastatin antibodies. Conclusion. We have developed a simple, sensitive, specific, and quantitative ELISA for anticalpastatin antibodies that may have a high diagnostic value for RA. (J Rheumatol 2004;31:17-22) Key Indexing Terms:
RHEUMATOID ARTHRITIS
From the Department of Pathological Biochemistry, Hokkaido College of Pharmacy, Otaru; Department of Orthopedic Surgery, Toyama Medical and Pharmaceutical University, Toyama; Seikagaku Corporation, and the Department of Internal Medicine, Teikyo University School of Medicine, Tokyo; and Hino Hospital, Osaka, Japan. S. Iwaki-Egawa, PhD, Assistant Professor; Y. Watanabe, PhD, Professor, Pathological Biochemistry, Hokkaido College of Pharmacy; F. Nakazawa, MD, PhD, Department of Orthopedic Surgery, Toyama Medical and Pharmaceutical University; K. Miyazaki, PhD; A. Ochiai, PhD, Seikagaku Corporation; S. Hirohata, MD, PhD, Associate Professor, Department of Internal Medicine, Teikyo University School of Medicine; M. Shimizu, MD, PhD, Hino Hospital; H. Matsuno, MD, PhD, current appointment: Professor, Department of Biomedical Engineering, Toin University of Yokohama; K. Yudoh, MD, PhD, current appointment: Lecturer, Department of Bioregulation, Institute of Medical Science, St. Marianna University of Medicine, Kawasaki. Address reprint requests to Dr. S. Iwaki-Egawa, Department of Pathological Biochemistry, Hokkaido College of Pharmacy, 7-1 Katsuraoka-cho, Otaru 047-0264, Japan. E-mail: sachiko@hokuyakudai.ac.jp Submitted January 28, 2003; revision accepted June 27, 2003. |