Clinical evaluation of a new quantitative enzyme-linked immunosorbent assay for anti-dsDNA antibodies measured in patients with systemic lupus erythematosus

Abstract

Background: The measurement of autoantibodies specific for double-stranded DNA (anti-dsDNA) is a useful tool for the diagnosis and prognosis of systemic lupus erythematosus (SLE). A quantitative enzyme-linked immunosorbent assay (ELISA) for anti-dsDNA antibodies has recently become available for the determination of anti-dsDNA antibodies. The aim of this study was to evaluate the clinical performance characteristics of this assay in patients with inactive or active SLE. Methods: Serum samples from patients with inactive (n=65) or active (n=112) SLE were tested for anti-dsDNA autoantibodies using 2 methods from Euroimmun AG (Lübeck, Germany) - a new ELISA anti-dsDNA assay and the currently available Crithidia luciliae indirect immunofluorescent test (CLIFT). In addition, the levels of the complement components C3 and C4 biological markers associated with SLE disease activity were measured by nephelometry in the sera from all patients. Results: The sensitivity and specificity of the anti-dsDNA ELISA assay for discriminating between patients with inactive or active SLE were 93.54% and 67.69%, respectively. Among all patients (n=177), there was a weak concordance (κ=0.264) between antidsDNA results by the ELISA and CLIFT assay. However, a significant inverse correlation was found with complement components levels. In addition, area under the curve (AUC) values for anti-dsDNA as well as C3 and C4 assays decreased in the following order: 0.901 (ELISA for anti-dsDNA autoantibodies)>0.734 (C3)>0.723 (C4)>0.650 (CLIFT for anti-dsDNA autoantibodies). Conclusions: Our results show the ELISA for anti-dsDNA autoantibodies is significantly more sensitive and specific than any of the other assays we evaluated for discriminating between patients with inactive or active SLE. Moreover, the inverse correlation between ELISA anti-dsDNA autoantibody and complement levels suggests that anti-dsDNA results by the Euroimmun ELISA may be promising for monitoring disease activity in patients with SLE.