Analytical and clinical comparison of four SLE-associated autoantibodies in different autoimmune diseases

Autoantibodies associated with systemic lupus erythematosus (SLE) are often present in patients with a variety of autoimmune diseases, affecting the diagnosis and differentiation of the diseases. In this study, the positive rates and diagnostic efficiencies of anti-dsDNA, anti-nucleosome, anti-ribosomal P and anti-C1q antibodies were analysed in 216 SLE patients, 323 rheumatoid arthritis (RA) patients, 87 Sjogren's syndrome (SS) patients, 45 patients with other autoimmune diseases (OAD) and 52 healthy controls (HC). In addition to being high in SLE patients, the serum levels of anti-dsDNA and anti-nucleosome antibodies were also significantly higher in SS patients compared with OAD (P = 0.008, < 0.001). The ROC-AUCs for the four SLE-associated autoantibodies in distinguishing SLE patients from SS patients were lower than those in distinguishing SLE patients from HC. Therefore, SLE-associated autoantibody-positive SS patients represent a less studied and heterogeneous population, as these antibodies are also present in approximately 15% of all SS patients. Compared with SLE-associated autoantibody-negative SS patients, SS patients who were positive for SLE-associated autoantibodies were more likely to be positive for anti-nRNP/Sm autoantibodies (30.77% vs. 4.05%, P = 0.001). Oral ulcerations, rampant dental and pulmonary involvement were more frequent in SS patients who were positive for SLE-associated autoantibodies than in those who were negative for these autoantibodies (P = 0.018, 0.004 and < 0.001). In conclusion, SLE-associated autoantibody-positive SS patients represent a heterogeneous population, characterized by unique autoantibody profiles and clinical manifestations. This study may provide new insights for diagnostic refinement between SLE and SS patients.