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Anti-Sa antibody in Chinese rheumatoid arthritis
1Chinese Institute of Medical Science, Peking Union Medical College, Department of Rheumatology and Immunology, PUMC Hospital, Beijing, China.
Objective:
To test anti-Sa antibody in different autoimmune connective tissue diseases and analyze the relationship between Sa antibody and clinical manifestations and laboratory tests in rheumatoid arthritis.
Method:
Sa antigen was extracted from human placenta. Anti-Sa antibody was tested in 40 normal people and 478 connective tissue disease (CTD) patients using Western Blotting (WB).
Results:
Sa antigen was a protein with molecular weights of 50 kD and 55 kD. Anti-Sa antibody was positive in 31.9% (61/191) rheumatoid arthritis (RA), 3.0% (2/67) Sjögren's syndrome (SS), 4.3% (2/46) systemic lupus erythmatosus (SLE) and 0% (0/66) Behcet's disease, 0% (0/60) polymyositis/dermatomyositis (PM/DM), 0% (0/66) other CTD and 0% (0/40) normal controls. Anti-Sa antibody was different from other auto-antibodies in RA. In rheumatoid arthritis its sensitivity, specificity, positive prediction rate, negative prediction rate were 31.9%, 98.6%, 93.8% and 68.5% respectively. Anti-Sa antibody positive patients were significantly different from anti-Sa antibody negative patients in moming stiffness, ESR, ANA and X-ray grade.
Conclusion:
Anti-Sa antibody was a new auto-antibody for the diagnosis of RA. Anti-Sa antibody positive patients seem to have more serious inflammation and more advanced disease process.