Clinical implications of autoantibodies to extractable nuclear antigens in rheumatoid arthritis patients in tertiary care hospital in Riyadh, Saudi Arabia

Abstract

The purpose of this study was to assess the prevalence of autoantibodies against extractable nuclear antigens (ENAs), anti-Ro/SSA, anti La/SSB, anti Jo-1, ribo-nucleoproteins (anti UI-RNP) and antibodies to Smith (anti-Sm) in rheumatoid arthritis (RA) patients and to detect the relationship between the existence of these autoantibodies and clinical presentation, radiological damage, and disease activity markers. The study, included 57 RA patients and 35 normal controls, was conducted in Al-Quwayiya General Hospital. Sera were obtained from patients and controls to carry out Hs-CRP, ESR, RF factors, ANA and ACPA IgG. Anti-Sm, anti-U1-RNP, anti-Ro/SSA, anti-La/SSB, and anti-Jo-1 were measured using the Alegria® assay. ESR was 23.8±6.5, while CRP was 16.19±7.15 in RA patients. RF was detected in 23 (40.35%) patients and ACPA in 54 (94.73%), while ANA was positive in 14 (24.56%) cases. Anti-Ro/SSA was detected in 8 (14.03%) patients, anti-La/SSB in 3 (5.26%), anti-Jo-1 was found in 2 cases (3.50%), and anti-RNP in 1 (1.75%). Anti-Ro/SSA had a significant negative relationship with sex (r=-0.220, P=0.001), but a positive correlation was observed with sicca symptoms (r=0.149, P=0.02). Anti-La/SSB antibodies correlated positively with swollen joint count (r=0. 0.225, P=0.001), tender joint count (r=0.219, P=0.001) and ANA (r=0.367, P < 0.001). Anti-Jo-1 antibodies showed a significant positive correlation with interstitial lung disease (r=-0.429, P≤0.001). Anti-Ro/SSA had a significant positive correlation with RF titer (r=0.259, P < 0.001) and ANA (r=0.498, P < 0.001). Anti-La/SSB had significant positive correlation with ANA (r=0.372, P < 0.001). Anti-Jo-1 showed a significant positive correlation with RF titer (r=0.141, P < 0.040) and ANA (r=0.249, P < 0.001). Anti-RNP showed a significant positive correlation with ACPA titre (r=0.288, P < 0.001) and ANA (r=0.159, P < 0.018). We conclude that ENA autoantibodies are crucial and need to be correlated with clinical diagnosis and other serological testing for early diagnosis and intervention of the RA.