Diagnostic value of antibody immunoblotting detection in rheumatoid arthritis patients

Objective. To assess the diagnostic value of antinuclear antibody (ANA) profiling in rheumatoid arthritis by immunoblotting. Materials and methods. In total, 46 patients with rheumatoid arthritis (RA) with a mean age of 34.6 years (21.3–63.2) were observed. The disease duration was 11.2 years (3.7–19.8); the activity according to DAS 28 was 3.15 ± 1.36 (3.05–3.61) points. The RA diagnosis was based on generally accepted clinical guidelines. The control group included 28 patients with osteoarthritis. Laboratory examinations were conducted using a set of reagents to determine IgG antibodies to nuclear antigens by immunoblotting. Results. The RA patients showed an increased level of antibodies to the RNP/Sm antigen, with its frequency being significantly higher than in the control group ( p = 0.007). The most specific testomes for diagnosing RA were anti-RNP/Sm (specificity 96%, sensitivity 25%) and antibodies to the recombinant antigen (sensitivity 25%, specificity 88.1%). The method of ROC analysis found that the value of anti-RNP/Sm = 0 is the point corresponding to the optimal ratio of sensitivity/specificity. This value corresponds to a sensitivity of 50% and a specificity of 73.8%. Conclusion. The studied laboratory tests, as a rule, showed high specificity, but rather low sensitivity. The most specific test for RA is anti-RNP/Sm. The conducted ROC analysis showed that the anti-RNP/Sm test has an average quality index for diagnosing RA.