The presence of antibodies to cyclic citrullinated peptide (CCP) has high specificity in the diagnosis of rheumatoid arthritis (RA). Hepatitis C virus (HCV) infection may induce extra-hepatic manifestations, such as polyarthritis that mimic RA. The aim of this study was to determine the prevalence of anti-CCP antibodies in HCV-infected patients with or without arthritis, rheumatoid factor (RF), or cryoglobulinemia and to investigate whether anti-CCP antibodies may be helpful in discriminating patients with RA from patients with HCV-associated arthropathy. A total of 44 patients with RA, 34 patients with HCV infections, and 42 control patients with non-RA rheumatic diseases were recruited for the study. Anti-CCP antibody levels were determined by enzyme-linked immunosorbent assay. We found that, consistent with other reports, patients with RA were more likely to have high titers of anti-CCP antibody than HCV-infected or control patients. A significant number of HCV-infected patients with neither RF nor cryoglobulinemia were also positive for anti-CCP antibodies (the three positive values were 36.10, 8.65, and 5.83 U/ml, P<0.01 compared with the control patients). The presence of cryoglobulinemia and/or RF in HCV-infected patients did not affect the anti-CCP outcomes. Although anti-CCP antibodies remain to be a very useful tool in discriminating RA from non-RA, HCV-infected patients with neither RF nor cryoglobulinemia may have anti-CCP antibodies. Because of limited patient numbers, this tentative conclusion may need further confirmation with inclusion of more patient population.
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