Anti-nucleosome antibodies in patients with systemic lupus erythematosus: potential utility as a diagnostic tool and disease activity marker and its comparison with anti-dsDNA antibody.
OBJECTIVE
To compare the utility of anti-nucleosome antibodies and anti-dsDNA antibodies in diagnosis of Systemic Lupus Erythematosus (SLE) and as a marker of disease activity.


METHODS
This is a hospital based observational study among 40 (37 females and 3 males) selected cases of SLE (> or = 4 ACR criteria) and 80 control. 40 cases of other systemic autoimmune disease (SAD) [e g. 29 cases of Rheumatoid arthritis, 4 cases of Systemic sclerosis/scleroderma, 4 cases of Sjögren syndrome, 3 cases of MCTD and 40 Healthy blood were taken as control. From each patient venous blood samples were collected and submitted for anti-nucleosome and anti-dsDNA antibodies assay by enzyme linked immunosorbent assay (ELISA).


RESULTS
Anti-nucleosome antibodies were positive in 19 (47.5%) SLE, 02 (05%) other SAD and none of the healthy persons. Anti dsDNA antibodies were positive in 15 (37.5%) SLE patients, 07 (17.5%) other SAD and 01(2.5%) healthy persons. For diagnosis of SLE, sensitivity of anti-ds DNA and anti-nucleosome antibody was found to be 37.5% and 47.50% respectively. The specificity of anti-nucleosome was 100% and that of anti-dsDNA was 97.50%. So, anti-nucleosome antibody test is more specific and more sensitive for diagnosis of SLE than anti-dsDNA. When SLE cases were compared with SAD, sensitivity of anti-dsDNA and anti-nucleosome antibody, for diagnosis of SLE, found to be 37.50% and 47.50% respectively but the specificity of anti-nucleosome was 95% and that of anti-dsDNA was 82.50%. Both antibodies show positive correlation with SLEDAI score .The correlation coefficient was stronger for anti-dsDNA antibodies (r = +0.550, P = < .001) than anti-nucleosome antibodies (r = +0.332, P = < .05) CONCLUSIONS: Anti-nucleosome antibodies show higher positivity than anti-dsDNA antibodies among SLE than other SAD and healthy population. Anti-nucleosome antibodies are more sensitive and specific for the diagnosis of SLE than anti-dsDNA antibodies. Anti-nucleosome and anti-dsDNA both show positive correlation with SLEDAI. But anti-dsDNA antibodies show stronger correlation with SLEDAI than anti-nucleosome. So, anti-nucleosome antibodies can be used as an additional marker for diagnosis of SLE and SLE disease activity.