AB1225 Antibodies against heterogeneous nuclear ribonucleoproteins (RA33) may have a diagnostic and prognostic value in rheumatoid arthritis, particularly when other serological tests are negative
Authors: V.A. Aleksandrov, L.N. Shilova, A.V. Alexandrov
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> The high frequency of detection of antinuclear antibodies in rheumatoid arthritis (RA), although predominantly in low titres, allows us to consider the possibility of using varieties of these antibodies (primarily antibodies to RA-33) markers of RA especially in the early stages of the disease. <h3>Objectives</h3> To study the frequency of occurrence and determine the prognostic significance of antibodies to RA-33 in RA patients. <h3>Methods</h3> 57 RA patients were examined (mean age 50.5±10.1 years). The patients with the developed stage of the disease (47.4%) prevailed, the average activity (DAS28=3.2–5.1) of the pathological process (86%); with the second radiographic stage (42%) and functional class 2 (77%). The antinuclear factor was determined in the indirect immunofluorescence reaction on the HEp-2 cell line (norm &lt;1:80), IgM-rheumatoid factor by the latex agglutination method (up to 20 IU/ml), antibodies (norm up to 20 U/ml) and antibodies of IgG class to RA33 antigen (norm up to 25 U/ml) by ELISA test. <h3>Results</h3> ANF was detected in 18 patients with RA (32%), and in 94.4% of cases (17 patients) a diagnostic titer of 1:80 and a diffuse type of glow of the nucleus were noted. The ANF titres did not correlate either with the activity of the disease or with extra-articular manifestations of RA (p&gt;0.1). Anti-RA33 was detected in 20 (35%) RA patients: 18 positive people (90%) had low positive anti-RA33 values (25 to 75 U/ml). In 35 (61.4%) of RA patients, anti-CCP was detected: 19 (33.3%) had low positive values (20 to 60 U/ml), 16 (28%) had highly positive values (more 60 U/ml). IgM-RF was detected in 26 (45.6%) patients in the values&gt;48 IU/ml, as well as in 17 (30%) patients with RA in the values from 24 to 48 IU/ml. 14 people (54%) of patients with high IgM-RF levels had systemic manifestations of RA. It should be noted that anti-RA33 was detected in 9 patients with seropositive for anti-CCP and in 11 patients with seronegative both for anti-CCP and IgM-RF. Thus, when the results of standard serological tests are negative, an additional study of anti-RA33 is recommended to diagnose seronegative RA. When assessing the prognostic significance of the available clinical and laboratory and instrumental data we have analysed the results of the study of anti-CCP, anti-RA33, as well as all data on the presence of X-ray erosions in patients with RA with magnetic resonance imaging or ultrasound examination of affected joints. The presence of erosion was noted in 23 (40.4%) RA patients. The frequency of detection of anti-CCP in RA patients was significantly higher in the presence of erosive lesions of joints (19 of 35 patients were positive by anti-CCP, compared with 4 of 22 patients, negative for anti-CCP, χ2=5.89, p=0.015). In the RA group of patients positive for a wide range of antibodies (IgM-RF, anti-CCP, anti-RA33), the signs of joint erosion were identified in 22 of 46 patients, and in isolated increase only anti-RA33 – in 1 patient out of 11 people in this group χ2=4.04, p=0.044). <h3>Conclusions</h3> In the presence of highly positive anti-CCP values, RA patients have a more unfavourable prognosis, while an isolated increase in anti-RA33 is associated with a "milder progression" of the disease and inversely proportional to erosive processes in the joints. <h3>Disclosure of Interest</h3> None declared