Clinical evaluation of a new quantitative enzyme-linked immunosorbent assay for detection of double-stranded DNA autoantibodies.

The measurement of autoantibodies specific for double-stranded DNA (anti-dsDNA) is a useful tool for the diagnosis and the prognosis of systemic lupus erythematosus (SLE). A new quantitative enzyme-linked immunosorbent assay (ELISA), ORG anti-dsDNA, is recently available for the determination of anti-dsDNA antibodies. The aim of this study was to evaluate the clinical performance of this new assay in a cohort of SLE patients. Seventy-five sera from SLE patients were tested by two methods for anti-dsDNA determination, ORG anti-dsDNA, and EliA anti-dsDNA. Normal controls were 60 sera from healthy subjects. Moreover, 37 sera from patients with non-SLE connective tissue diseases were tested in parallel. The levels of complement components (C3, C4, CH50) were measured by nephelometry. From SLE patients, 91% were positive against 9% in non-SLE patients and 2% in healthy subjects. The sensitivity, specificity, and Youden test for SLE were 90%, 98%, and 88%, respectively. The Yule test (1%) indicated a close association with the disease. The comparison with EliA anti-dsDNA showed a moderate concordance between the two tests in the group of SLE (kappa = 0.51) and a good concordance in the non-SLE group (kappa = 0.89). A significant inverse correlation was found with complement components levels, biological markers associated with disease activity. Our results show this new assay as sensitive and specific for the diagnosis of SLE. Moreover, the correlation with markers associated with disease activity makes it promising for clinical use.