Anti-nucleosome Antibodies In Systemic Lupus Erythematosus

BACKGROUND: Antinucleosome antibody (AnuA) has recently heen described in patients with systemic lupus erythematosus (SLE) and it has been suggested that its presence is associated with lupus nephritis(LN).OBJECTIVE: To study the frequency and disease specificity of AnuA reactivity in diverse connective tissue diseases (CTD). To assess the prevalence and clinical associations of AnuA in SLE. To compare the utility of auto-antibodies for the diagnosis of SLE.METHODS: We included 120 consecutive patients (107 female) with SLE (four or more ACR criteria). As control groups we included 30 healthy blood donors and 55 patients with 7 other CTD. Disease activity was assessed using the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI). A venous blood sample was drawn to measure AnuA by enzyme-linked immunosorbent assay (ELISA). The groups were evaluated for AnuA and for clinical, humoral parameters (hemoglobin, blood cell count, urinanalysis, ESR, ANA, CIC, ALT, C3C4, ALB) and other auto-antibodies [anti-double-stranded DNA (anti-dsDNA), anti-Smith (anti-Sm), anti-nuclear (ANA), anti-histones (AHA), anti-cardiolipin (ACL)].RESULTS: The prevalence of AnuA in SLE patients and controls was 55.83% and 4.71% respectively, 35% and 1.18% for anti-dsDNA, and 24.17% and 0% for anti-Sm. AnuA had a sensitivity of 55.83% and specificity of 95.29% for SLE diagnosis. AnuA showed the highest correlation with disease activity, especially in patients negative for anti-dsDNA antibodies. The levels of AnuA strongly correlated with SLEDAI (t = 2.171, P < 0.05), but inversely correlated with serum complement (C3, C4) levels in anti-dsDNA negative SLE patients (in AnuA positive group than (vs) AnuA negative group, C3: 0.53 +/- 0.24 g/L vs 0.79 +/- 0.23 g/L, p < 0.001; C4: 0.10 +/- 0.04 g/L vs 0.18 +/- 0.04 g/L, p < 0.001). Arthritis, ulceration and albuminuria were more altered in AnuA positive group than (vs) AnuA negative group. AnuA also showed strong association with renal and liver damage.CONCLUSION: The measurement of AnuA appears to be a useful addition to the laboratory tests that can help in the diagnosis and treatment of SLE, especially in patients who are negative for anti-dsDNA antibodies. Our data suggest that the AnuA may be a sensitive and specific for SLE, but isn't a marker for an increased risk of lupus nephritis. Simultaneous detection of AnuA, anti-dsDNA, anti-Sm and ANA can notably improve the specificity.