Antibody clustering helps refine lupus prognosis.

Objective Our aim was to investigate a possible association between patterns of anti-dsDNA antibody isotypes (IgG, IgM, and IgA), rheumatoid factor (RF) isotypes (IgG, IgM, IgA), and IgG anti-C reactive protein (CRP) and systemic lupus erythematosus (SLE) disease activity (SLEDAI). Methods Our study group included 98 patients, 86 women and 12 men, with a mean SLEDAI score of 7.9 ± 4.1. We divided the patients into 4 groups by the serum anti-dsDNA antibody isotype intensity level. Results We found that patients in group 1 (IgG > IgM, 42 patients) had a statistically significantly higher SLEDAI score than group 2 (IgG P = 0.0012), group 3 (IgG = IgM, 8 patients) (10.57 ± 4.62 versus 6.2 ± 1.98, P = 0.04), and group 4 (none, 35 patients) (10.57 ± 4.62 versus 6 ± 1.5, P = 0.0001). SLE patients with IgG RF or IgM RF isotype present had a significantly higher SLEDAI score compared with those without IgG RF or IgM RF (10.57 ± 4.8 versus 7.6 ± 4.1, P = 0.03, 10.6 ± 5 versus 7.6 ± 3.9, P = 0.046). The presence of IgA RF isotype was not associated with a higher SLEDAI score. IgG anti-CRP did not correlate differentially with SLEDAI scores. Conclusions A combination of high-titer IgG anti-dsDNA with a positive RF of IgM isotype may serve as a marker for more active SLE.