Noncognate binding to histones of IgG from patients with idiopathic systemic lupus erythematosus

Meta-analysis as a diagnostic tool for predicting disease onset and/or activity in systemic lupus erythematosus

Systemic lupus erythematous (SLE) is a relatively rare disorder with prevalence rates between 5 and 50 per 100,000 population. This means performing any epidemiological analysis in a specific research center is difficult, due to the low number of cases within any one location. There is a need for biomarkers and diagnostic aids to monitor SLE disease activity and severity prior, during, and after treatment. Many specialist lupus clinics worldwide have published trials following in detail small numbers of patients that have been monitored for a disease biomarker, e.g., an autoantibody against a self-molecule in prospective and retrospective studies. They have then attempted to correlate autoantibody levels against an autoantigen with disease activity, e.g., nephritis development. The results are often inconclusive with the conclusion "the autoantibody may be useful in monitoring disease activity." Meta-analysis is a statistical technique that can be used for combining the findings of multiple studies to add power to any tentative conclusion proposed by individual studies. Here, we describe a method for analyzing biomarkers of interest as predictors of disease activity, using anti-C1q autoantibodies as an example.

Anti-topoisomerase I (anti-Scl-70) antibodies in patients with systemic lupus erythematosus

OBJECTIVE

To investigate the presence and clinical significance of anti-Scl-70 antibodies in patients with systemic lupus erythematosus (SLE).

METHODS

Levels of antibodies against Scl-70 were determined by a commercial clinical enzyme-linked immunosorbent assay (ELISA) during routine evaluation. Results were verified by an additional ELISA with a characterized bovine Scl-70, by ELISA with a recombinant human topoisomerase I, by Western blot, and by double diffusion in agar gel. Disease activity was estimated retrospectively by the Systemic Lupus Activity Measure (SLAM).

RESULTS

Of 128 consecutive SLE patients, 25% were positive for anti-Scl-70 antibody; this antibody activity was cognate in nature. No SLE patient could be classified as also having systemic sclerosis. The levels of anti-Scl-70 were significantly correlated with the SLAM score for the entire cohort (r = 0.563, P < 0.001) and for 7 individual patients with multiple longitudinal measurements (r = 0.755-0.951, P < 0.001; n = 6) (r = 0.378, P < 0.05; n = 1). A significant correlation was also found between the levels of anti-Scl-70 and anti-double-stranded DNA antibodies (r = 0.558, P < 0.001). Patients with anti-Scl-70 had significantly higher risk of pulmonary hypertension (P < 0.01) and renal involvement (P < 0.001) than patients without this antibody.

CONCLUSION

Anti-Scl-70 antibody is present in a significant subset of patients with SLE. For this subset, it offers a good correlate of disease activity and suggests increased risk for pulmonary hypertension and nephritis.