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Patients with systemic lupus erythematosus (SLE) often develop a wide variety of serological manifestations including the presence of antibodies to double-stranded DNA (anti-dsDNA). Positivity for anti-dsDNA constitutes one of the laboratory criteria for the diagnosis of SLE and is therefore clinically relevant. We analyzed the diagnostic accuracies of four commercial anti-dsDNA immunoassays and compared the results with a recently established surface plasmon resonance (SPR) biosensor chip with covalently chip-immobilized dsDNA. The anti-dsDNA measurements were performed retrospectively in 50 patients with clinically proven SLE, 39 patients with other autoimmunopathies and 20 healthy controls. Data were evaluated by Receiver-Operator Characteristic (ROC) analysis, with special regard to SLE patients suffering from lupus nephritis. The ROC analyses for the four immunoassays and the SPR biosensor resulted in the following area-under-the-curve (AUC) and diagnostic efficiency (DE) values in descending order: Bindazyme AUC, 0.89; DE, 0.88; ELiA AUC, 0.89; DE, 0.86; SPR biosensor AUC, 0.82; DE, 0.80; Farrzyme AUC, 0.77; DE, 0.77; Farr AUC, 0.77; DE, 0.70. When considering the 22 nephritis SLE patients the following AUC were observed: Bindazyme 0.98; EliA 0.95; SPR biosensor 0.93; Farr 0.89; Farrzyme 0.88. Although various methodologies for the determination of anti-dsDNA were compared, the overall diagnostic accuracy was found satisfactory in all immunoassays. Best data were found for the Bindazyme assay. We referenced the measurements to our in-house SPR biosensor device which showed good AUC and DE values. When optimized, this technique, allowing to monitor antigen/ antibody interactions in real-time, may add a new analytical quality to the existing methods, potentially beneficial in diagnosis and clinical monitoring of SLE. [ABSTRACT FROM AUTHOR]

To determine whether the serum levels of anti-double strand DNA (anti-dsDNA) autoantibodies detected using a newly developed fluorescence immunoassay (FIA) in patients with systemic lupus erythematosus (SLE) correlated more with clinical parameters, such as SLE disease activity index (SLEDAI), complement and the occurrence of nephritis when compared with traditional enzymelinked immunosorbent assay (ELISA), we prospectively collected 124 serum samples from 31 patients who had juvenile-onset SLE and were regularly monitored every 2 months at our outpatient clinic. At every visit, clinical manifestations and laboratory parameters were assessed and the SLEDAI was determined. Correlation analyses between the two different measurements of antidsDNA antibodies and SLEDAI, serum complement levels and the occurrence of nephritis were performed. The results showed that anti-dsDNA autoantibodies detected using both ELISA and FIA significantly correlated with SLEDAI, and significantly and inversely correlated with the serum levels of C3 and C4. FIA had significantly higher correlation with SLEDAI and C4 than did ELISA. The mean values of anti-dsDNA antibodies detected using FIA in patients with nephritis were significantly higher than in those without nephritis. In contrast, the values of anti-dsDNA antibodies detected using ELISA did not show significant differences between these two groups. We conclude that FIA had better correlation with SLEDAI, C4 and the occurrence of nephritis, and comparable correlations with C3 that were similar to the results found using ELISA. Thus, it is worthwhile developing the FIA method for clinical evaluation of disease activity in SLE patients. [ABSTRACT FROM AUTHOR]