Anti-nucleosome antibodies as a disease marker in systemic lupus erythematosus and its correlation with disease activity and other autoantibodies

Background: Detection of anti-nucleosome antibodies (anti-nuc) in patients with systemic lupus erythematosus (SLE) has been well established and it is claimed that their presence is associated with disease activity.
Aims: The aim of this study is to evaluate the incidence of anti-nuc antibodies and to correlate them with disease activity and its association with other autoantibodies like anti-nuclear antibodies (ANA), anti-double stranded DNA (anti-dsDNA), anti-histone antibodies (AHA), as well as autoantibodies to histone subfractions like H1, (H2A-H4) complex, H2B, and H3.
Methods: This cross-sectional study included 100 SLE patients referred from the Rheumatology, Dermatology, and Nephrology Departments. SLE disease activity was evaluated by using SLE-Disease Activity Index (SLEDAI) score. A patient was defined as having active SLE when the SLEDAI score was more than 5.0. Fifty normal controls were also tested as a healthy control group. Anti-nuc antibodies, anti-dsDNA, and AHA were tested by Enzyme-Linked Immunosorbent Assay (ELISA) and ANA was detected by an indirect immunofluorescence test.
Results: All patients studied were in an active stage of disease and were untreated, of which 44 patients had renal biopsy-proven kidney involvement, which was categorized as lupus nephritis (LN) and 56 patients did not show any renal manifestations (SLE without LN). Anti-nuc antibodies were positive in 88%, anti-dsDNA in 80%, and AHA in 38% of the cases. ANA was positive in all SLE patients studied. None of the normal controls was found to be positive for these antibodies. Although a slightly higher incidence of autoantibodies were noted in LN, there was no statistical difference noted between LN and SLE without LN groups for anti-nuc and anti-dsDNA antibodies (p > 0.05). A higher incidence of autoantibodies to ANA specificities were noted in anti-nuc positive cases, but there was no statistical difference between anti-nuc positive and anti-nuc negative cases for ANA specificities among LN and SLE without nephritis groups (p > 0.05).
Conclusions: Anti-nuc antibody detection could be a better tool for the diagnosis of SLE. Although there was no significant difference in LN and SLE without LN groups, this study suggests that anti-nuc detection can be useful as an additional disease activity marker to other laboratory tests.

Keywords
Systemic lupus erythematosus, anti-nucleosome antibodies, anti-double stranded DNA antibodies, anti-histone antibodies, lupus nephritis, SLE without nephritis