High diagnostic value of anticalpastatin autoantibodies in RA detected by ELISA using human erythrocyte calpastatin as antigen

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J Rheumatol. 2004 Jan;31(1):17-22.

High diagnostic value of anticalpastatin autoantibodies in rheumatoid

arthritis detected by ELISA using human erythrocyte calpastatin as

antigen.

Iwaki-Egawa S, Matsuno H, Yudoh K, Nakazawa F, Miyazaki K, Ochiai A,

Hirohata S, Shimizu M, Watanabe Y.

Department of Pathological Biochemistry, Hokkaido College of Pharmacy,

Otaru, Japan.

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 Sjogren'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.

PMID: 14705213