Anti-citrullinated peptide antibodies (ACPA) play an important role in rheumatoid arthritis (RA) diagnosis. In our study, we sought to assess the potential diagnostic value of synthetically manufactured peptides that contain epitopes believed to have a pathogenic role in RA.
Serum samples from RA patients and healthy controls were obtained. Two synthetic peptides were manufactured containing the common epitopes considered to play a pivotal role in the RA pathogenesis including the antigenic epitopes of filaggrin, beta-fibrinogen, collagen, vimentin and enolase. Three different ELISA kits for citrullinated peptides (namely: CCP3, Cit-ME-Vim and Cit-ME-Eno) were tested and compared. To assess the diagnostic value of the three ELISA tests, for each test the optical densities (OD) were recorded. The statistical power of each test was calculated measuring the area under the curve (AUC) corresponding with each peptide.
Serum levels of ACPA recognized by the commercial CCP3 in RA and healthy controls were 1.31 ± 0.88 optic density units (ODU) and 0.21 ± 0.11 ODU, respectively. Cit-ME-Vim levels were 0.55 ± 0.46 ODU in RA subjects and 0.17 ± 0.182 ODU in healthy controls whereas Cit-ME-Eno was 0.61 ± 0.65 ODU in RA subjects and 0.22 ± 0.20 ODU in healthy controls. AUC results were as follows: CCP3, 0.89 [95%CI 0.75-0.87]; Cit-ME-Vim, 0.76 [95%CI 0.69-0.82]; Cit-ME-Eno, 0.73 [95%CI 0.65-0.79]. Statistical significance for all results was achieved (p < .0001). Sensitivity values for each kit are as follow: CCP3 70.42%; Cit-ME-Vim 63.38%; Cit-ME-Eno 40.85%, and specificity 91% for all tests.
Our study supports the presence of an added value for the Cit-ME-Vim peptides in the diagnosis of RA. Further studies are needed to replicate such findings.