Background Rheumatoid arthritis (RA) is a chronic inflammatory disease affecting the synovial joints, often with a progressive and destructive course, associated with the production of wide range of autoantibodies, and their detection has diagnostic and prognostic implication.
Objectives This study was to estimate the diagnostic value of antibodies against cyclic citrullinated peptide (ACCP) and nuclear antigen RA33 of the IgA rheumatoid factor (RF) versus the value of routinely used profile of autoantibodies in diagnostic work-up of RA.
Methods We identified 230 patients with RA prehistory of varying duration. The control group was comprised of 96 patients, including patients with seronegative spondyloarthropathies (SpA), Psoriatic Arthritis (PsA) and diffuse connective tissue diseases, as well as sex and age matched healthy controls. Serum levels of IgM and IgA RF, antibodies against cyclic citrullinated peptide (ACCP), antibodies against RA33 antigen (ARA33) and antinuclear factor (ANF) were measured in all patients and controls.
Results Diagnostic sensitivity of ACCP equaled 81%, IgM RF - 76%, IgA RF - 46%, ARA33 - 36% and ANF - 29%. ACCP was significantly more commonly associated with IgM RF. Among RF seronegative patients ACCP were found in 37% cases with 26 IU/Ml detection threshold, and in 26% - with 32 IU/Ml, allowing to increase diagnostic specificity of the test up to 93% with the increment of diagnostic threshold. Incidence of ARA33 was not significantly different among the RF and ACCP positive or negative subgroups, thus making ARA33 an independent RA marker. Specificity of this marker was 83,4%, thus making it inferior to RF and ACCP by a composite of diagnostic characteristics.
Conclusions The measurement of RA33 is a rational approach at the next second stage of serologic testing work-up in suspected cases of RA onset, when initial RF and ACCP tests were negative.
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Acknowledgements All employees of Department of Rheumatology National Center of Cardiology and Internal Medicine, Bishkek, Kyrgyz Republic
Disclosure of Interest None declared
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