Anti-CCP antibodies, rheumatoid factors and anti-keratin antibodies: clinical value in established rheumatoid arthritis

SUMMARY Background : It is well documented that in early rheumatoid arthritis, anti-CCP antibodies have better diagnostic value than rheumatoid factors and anti-keratin antibodies. However, their role is less well defined in patients with established or long duration disease. Aim : To evaluate and to compare diagnostic performances of antiCCP , anti-keratin, IgM and IgA rheumatoid factors in established rheumatoid arthritis. Methods : In a cross-sectional study, 90 patients with established rheumatoid arthritis and 100 controls were tested for these autoantibodies. The association of these markers with disease activity and severity was investigated. The sensitivity and specificity were calculated for each of four tests, using the clinical diagnosis as the gold standard. Results : The anti-CCP and IgM rheumatoid factor exhibited the best diagnostic value. None of the tested antibodies had any significant association with the disease activity score (DAS28). After adjustment by multiple linear regression, only anti-CCP positivity was found to be significantly associated with erosive disease. Conclusion : In long duration rheumatoid arthritis, anti-CCP and IgM rheumatoid factor have similar diagnostic value. However antiCCP are useful in seronegative patients. They are also a reliable marker of severe erosive disease.