Research article

Diagnostic value of anti-cyclic citrullinated peptide antibodies in Greek patients with rheumatoid arthritis

Ioannis Alexiou¹ , Anastasios Germenis² , Athanasios Ziogas¹ , Katerina Theodoridou² and Lazaros I Sakkas¹

¹Department of Rheumatology, Thessaly University School of Medicine and Hospital, 412 22 Larisa, Greece

²Department of Immunology and Histocompatibility, Thessaly University School of Medicine and Hospital, Larisa, Greece

author email corresponding author email

BMC Musculoskeletal Disorders 2007, 8:37doi:10.1186/1471-2474-8-37

Published:	20 April 2007

Abstract

Background

Anti-cyclic citrullinated peptide (anti-CCP) antibodies have been of diagnostic value in Northern European Caucasian patients with rheumatoid arthritis (RA). In these populations, anti-CCP antibodies are associated with the HLA-DRB1 shared epitope. We assessed the diagnostic value of anti-CCP antibodies in Greek patients with RA where the HLA shared epitope was reported in a minority of patients.

Methods

Using an enzyme-linked immunosorbent assay (ELISA) (CCP2) kit, we tested anti-CCP antibodies in serum samples from 155 Greek patients with RA, 178 patients with other rheumatic diseases, and 100 blood donors. We also determined rheumatoid factor (RF) and compared it to anti-CCP antibodies for area under the curve (AUC), sensitivity, specificity and likelihood ratios.

Results

Sensitivity of anti-CCP2 antibodies and RF for RA was 63.2% and 59.1%, and specificity was 95.0% and 91.2%, respectively. When considered simultaneously, the AUC for anti-CCP antibodies was 0.90 with 95% CI of 0.87 to 0.93 and the AUC for RF was 0.71 with 95% CI of 0.64 to 0.77. The presence of both antibodies increased specificity to 98.2%. Anti-CCP antibodies were positive in 34.9% of RF-negative RA patients. Anti-CCP antibodies showed a correlation with the radiographic joint damage. Anti-CCP-positive RA patients had increased the swollen joint count and serum CRP concentration compared to anti-CCP-negative RA patients (Mann-Whitney U test, p = 0.01, and p < 0.001, respectively). However, no correlation was found between anti-CCP antibodies and DAS28 score (r = 0.13, p = 0.12).

Conclusion

In Greek patients with RA, anti-CCP2 antibodies exhibit a better diagnostic value than RF and a correlation with radiological joint damage and therefore are useful in everyday rheumatology practice.