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The detection of anti-dsDNA antibodies plays an outstanding role in the diagnosis of systemic lupus erythematosus (SLE). However, the quality of methods used for SLE diagnosis may differ greatly. For this reason, we compared the diagnostic value of four commercial ELISAs (Farrzyme, Bindazyme, Orgentec and Varelisa) with that of the Farr radioimmunoassay (Farr-RIA) and the Crithidia luciliae immunofluorescence test (CLIF).
Each was used to test serum samples from SLE patients versus control groups of patients with other inflammatory diseases. CLIF and Farr-RIA proved to be highly specific for SLE (99% and 88%, respectively). The diagnostic sensitivity of Farr-RIA was high (85%), whereas CLIF was significantly less sensitive (68%). The diagnostic specificity of the four ELISAs was lower (71% to 78%). In contrast, the diagnostic sensitivity of 3 out of 4 ELISAs was comparable or higher than that of Farr-RIA. The Farrzyme ELISA had slightly greater diagnostic specificity (78%), but was less sensitive (70%) than other ELISAs. Anti-dsDNA antibody detection by Farrzyme ELISA, Farr-RIA and CLIF was associated with renal involvement and low levels of complement components C3 and C4. Anti-dsDNA antibodies measured by these three assays and two ELISA methods (Bindazyme and Orgentec) were related to disease activity.
These results confirm that there are notable quality differences between the studied antidsDNA antibody assays. CLIF and Farr-RIA are particularly valuable for SLE diagnosis.
With CLIF and Farr-RIA, positive anti-dsDNA antibody results were obtained almost exclusively in SLE patients. Consequently, positive anti-dsDNA antibody results by the ELISA tests most commonly used in routine laboratories should be confirmed by CLIF and/or Farr-RIA to establish the definitive diagnosis of SLE. The ELISA methods are highly sensitive and can be used to monitor disease activity in patients with an already confirmed
diagnosis of SLE.