What can we learn from the presence of anti-cyclic citrullinated peptide antibodies in systemic lupus erythematosus?

BACKGROUND

Anti-cyclic citrullinated peptide (anti-CCP) antibodies have proved to be a specific marker for the diagnosis of rheumatoid arthritis (RA). However, the antibodies can also be detected in other rheumatic diseases, especially systemic lupus erythematosus (SLE). Recent studies have shown anti-CCP antibodies are associated with erosive arthritis in SLE patients. Since erosive arthritis is not common in SLE and many patients with non-erosive arthritis also have anti-CCP antibodies, the clinical significance of anti-CCP antibodies in SLE needs to be further studied.

OBJECTIVE

To investigate the prevalence and clinical significance of anti-CCP antibodies in Chinese SLE patients.

METHODS

Serum samples from 138 SLE patients were examined for anti-CCP with the second generation anti-CCP detection kit. The associations of anti-CCP with clinical and laboratory features, especially arthritis, in such SLE patients were analyzed.

RESULTS

The prevalence of anti-CCP was 13.8% (19/138) in Chinese SLE patients. Seventy of 138 SLE patients had experienced arthritis, of whom 14 patients were anti-CCP+. Significantly, anti-CCP antibodies were more frequently found in SLE patients with arthritis than without arthritis (20% vs 7.4%, P<0.05). A statistical correlation between anti-CCP and rheumatoid factor (RF) was found in SLE patients with arthritis (r=0.36, P=0.002). The frequency of arthritis was significantly higher in SLE patients with anti-CCP than without (73.7% vs 47.1%,P<0.05). Eight out of 138 SLE patients showed joint erosions on radiographs. When compared with anti-CCP- patients, erosive arthritis occurred more often in anti-CCP+ patients (35.7% vs 5.4%, P<0.001). Interestingly, two patients without anti-CCP and RF who had erosive arthritis were anti-RA33 antibodies positive. All of 8 SLE patients with erosive arthritis in our study fulfilled 1987 ACR criteria for RA. With regard to other clinical and laboratory features, there were no differences between SLE patients with arthritis and without or between anti-CCP+ patients and anti-CCP- patients.

CONCLUSIONS

Anti-CCP antibodies have a frequency of 13.8% in Chinese SLE patients and its presence is closely associated with the onset of arthritis and bone erosion.