Comparison of the diagnostic potential of three anti-citrullinated protein antibodies as adjuncts to rheumatoid factor and CCP in a cohort of South African rheumatoid arthritis patients

Purpose: A retrospective comparison of the prevalence and diagnostic value of anti-Sa, anti-CEP-1, and anti-MCV autoantibodies relative to those of the established autoantibodies, composite RF and anti-CCP-IgG used routinely for RA diagnosis as a component of the ACR 2010 criteria, in a cohort of disease-modifying anti-rheumatic drug naïve African RA patients (n = 75).

Methods: Serum concentrations of anti-Sa, anti-CEP-1 and anti-MCV autoantibodies were measured using ELISA procedures, while anti-CCP-IgG antibodies were determined by fluorescence enzyme immunoassay, and composite RF by latex-enhanced laser nephelometry.

Results: The seropositivity frequencies of anti-Sa, anti-CEP-1 and anti-MCV antibodies for the RA patients were 82, 72, 85%, respectively, while that of anti-CCP-IgG and RF was 87% for both. Overall, anti-MCV demonstrated the best specificity, positive predictive value (PPV), odds ratio and positive likelihood ratio of all the types of autoantibody tested.

Conclusion: These observations in this unique cohort of RA patients indicated novel associations of all three autoantibodies in regard to HLA-SE risk alleles, disease severity and tobacco use that were not reported before. Elevated anti-Sa titers designated a propensity of higher disease and high-risk alleles in our cohort. Anti-CEP-1 association with HLA-SE homozygosity and high-risk alleles is also novel in this group. Of note, measurement of anti-MCV antibodies on presentation, either as an adjunctive or even as a stand-alone test, surpassed all other biomarkers investigated here and, therefore, may add value to clinical management.