Synovial fluid levels of anti–cyclic citrullinated peptide antibodies and IgA rheumatoid factor in rheumatoid arthritis, psoriatic arthritis, and osteoarthritis

Authors


Abstract

Objective

To assess the levels of anti–cyclic citrullinated peptide (anti-CCP) and IgA rheumatoid factor (IgA-RF) in synovial fluids of patients with rheumatoid arthritis (RA), psoriatic arthritis (PsA), and osteoarthritis (OA).

Methods

Knee effusions of 29 patients with RA (23 women, 6 men; mean ± SD age 60 ± 15 years), 20 with PsA (6 women, 14 men; mean age 51 ± 12 years), and 19 with OA (9 women, 10 men; mean age 73 ± 11.8 years) were aspirated, tested for white blood cell (WBC) counts, centrifuged, and stored at −20°. Sera of 22, 11, and 12 of these patients with RA, PsA, and OA, respectively, were similarly stored. IgG anti-CCP and IgA-RF were detected by enzyme-linked immunosorbent assay. Erythrocyte sedimentation rate and C-reactive protein levels were used as measures of disease activity.

Results

Mean levels of synovial fluid anti-CCP and IgA-RF were significantly increased in RA joint effusions compared with PsA and OA (anti-CCP: 150 ± 134, 34 ± 29, and 24 ± 26 units, respectively [P < 0.003]; IgA-RF: 76 ± 77, 15.7 ± 10, and 18 ± 20 units, respectively). No significant difference was noted between OA and PsA. A significant correlation was found between synovial fluid anti-CCP and serum anti-CCP and IgA-RF. In patients with RA, a significant correlation was found between synovial fluid WBC counts and IgA-RF (P = 0.03) and serum IgA-RF (P = 0.008), but not between synovial fluid and serum anti-CCP levels. In RA patients, C-reactive protein correlated with serum IgA-RF.

Conclusion

Anti-CCP and IgA-RF were significantly increased in synovial fluid of RA in comparison with PsA and OA patients.

Ancillary