title: High diagnostic value of anticalpastatin autoantibodies in rheumatoid arthritis detected by ELISA using human erythrocyte calpastatin as antigen.
abstract: OBJECTIVE
  To develop a quantitative method of measuring autoantibodies against human calpastatin in rheumatoid arthritis (RA) and to determine their diagnostic value compared with other autoimmune and articular diseases.
  
  
  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.
  
  
  CONCLUSIONS
  We have developed a simple, sensitive, specific, and quantitative ELISA for anticalpastatin antibodies that may have a high diagnostic value for RA.
authors.affiliation: Department of Pathological Biochemistry, Hokkaido College of Pharmacy, Otaru, Japan. sachiko@hokuyakudai.ac.jp
authors.forename: Sachiko
authors.initials: S
authors.lastname: Iwaki-Egawa
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Matsuno
authors.forename: Kazuo
authors.initials: K
authors.lastname: Yudoh
authors.forename: Fujio
authors.initials: F
authors.lastname: Nakazawa
authors.forename: Kyousuke
authors.initials: K
authors.lastname: Miyazaki
authors.forename: Akira
authors.initials: A
authors.lastname: Ochiai
authors.forename: Shunsei
authors.initials: S
authors.lastname: Hirohata
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Shimizu
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Watanabe
mesh_terms: D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000175:diagnosis* / Q000276:immunology*; D001323:Autoantibodies / Q000097:blood*; D001324:Autoantigens / Q000276:immunology; D015153:Blotting, Western; D002135:Calcium-Binding Proteins / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D004912:Erythrocytes / Q000276:immunology; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007075:Immunoglobulin M / Q000097:blood; D008297:Male; D008875:Middle Aged; D010003:Osteoarthritis / Q000175:diagnosis / Q000276:immunology; D012680:Sensitivity and Specificity
chemical_list: D001323:Autoantibodies; D001324:Autoantigens; D002135:Calcium-Binding Proteins; D007074:Immunoglobulin G; D007075:Immunoglobulin M; C033668:calpastatin