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[Determination of antibodies against cyclic citrullinated peptide in rheumatoid arthritis].

The ability of the synthetic peptide IMG-5, that reproduces one of the antigenic determinants of the protein filaggrin, to show antigenic activity was studied when anti-cyclic citrullinated peptide antibodies (ACCPAb) to filaggrin were found in the serum samples of patients with rheumatoid arthritis (RA). The binding of IMG-5 to ACCPAb has been shown to be specific (dose-dependent and reversible). The serum samples from patients with RA, controls, and donors show a significant difference in the interaction of the synthetic peptide with ACCPAb (p < 0.005 and p < 0.0001, respectively). The level of IgM rheumatoid factor (RF) detected in patients with RA differs greatly from that in the controls. In the patients with RA versus the controls, the specificity of ACCPAb determination was as high as 87; and the sensitivity was 40.5%. When ACCPAbs were determined using the commercial kit CCP, the specificity and sensitivity were 94 and 47.3%, respectively. The specificity of RF detection was equal to 50% and the sensitivity was 70%. The sensitivity of the test using IMG-5 is a maximum in X-ray stage IRA (69.2%) and falls in its stage III (26.7%). On the contrary, the sensitivity of the commercial kit and RF determination increases from X-ray stage I (46.2 and 53.8%, respectively) to II (66.7 and 80%). The sensitivity of the used tests in varying RA activities has demonstrated that they are most effective in patients with moderate RA activity. The concurrent detection of ACCPAb and RF increases the probability of differentiating RA from other rheumatic diseases.