Anti-nucleosome antibodies as a disease activity marker in patients with systemic lupus erythematosus

To measure the level of anti-nucleosome antibodies in systemic lupus erythematosus (SLE) patients, to determine the sensitivity and the specificity of these antibodies in the diagnosis of the disease and to evaluate the relationship between the levels of anti-nucleosome antibodies, anti-dsDNA (double-stranded DNA) and SLE disease activity.

A cross-sectional study was conducted. All patients attended either a medical specialist clinic or were admitted to the medical wards of Hospital Universiti Sains Malaysia with the diagnosis of SLE (n = 90), other connective tissue diseases (n = 45) or were normal controls (n = 90) within the period from July 2004 until September 2005. They were tested for anti-nucleosome antibodies by enzyme-linked immunosorbent assay and anti-DNA antibodies by immunofluorescence. SLE disease activity was evaluated by SLE disease activity index (SLEDAI) score.

Out of 90 SLE patients, anti-nucleosome antibodies were positive in 47 (52.2%) patients, whereas these antibodies were positive in three (6.7%) patients with other connective tissue diseases. Anti-dsDNA antibodies were positive in 33 (36.7%) SLE patients, whereas these antibodies were positive in four (8.9%) patients with other connective tissue diseases. Anti-nucleosome antibodies were positive in 40 (97.6%) patients with active SLE, whereas these antibodies were positive in seven (14.3%) patients with inactive SLE. Anti-nucleosome antibodies had a stronger correlation than anti-dsDNA antibodies with SLEDAI score. There was a significant association between anti-nucleosome antibodies and disease activity.

Anti-nucleosome antibodies test is highly sensitive and specific for the diagnosis of SLE, especially when the anti-dsDNA antibodies are absent. They are additional disease activity markers in the assessment of SLE disease activity.