Antibodies against double-stranded DNA (dsDNA) are the main focus in the serological diagnosis of systemic lupus erythematosus (SLE). These antibodies can be found in 60% to 90% of patients, depending on the activity of the disease. Antibodies against nucleosomes are also an exclusive marker for SLE, provided that they are determined using a perfect test system whose target antigen must be free of histone H1, Scl-70 and other non-histone proteins.

Using an innovative biochemical preparation, researchers at EUROIMMUN AG have developed a new test system that exceeds the diagnostic quality criteria of all conventional Anti-dsDNA ELISA by far (Anti-dsDNA-NcX ELISA). The secret of the innovation lies in the use of highly purified nucleosomes as the new linking substance. Since nucleosomes have a strong adhesive ability, even the smallest concentration of these is highly suited to couple isolated dsDNA to the surface of a microplate well. Poly-L-lysine and potamine sulphate have fallen into disuse, many false positive results are prevented, the specificity of the ELISA amounts to values which equal those of the indirect immunofluorescence test using Crithidia luciliae! In a clinical comparison study using 378 samples from patients with rheumatic diseases (209 of these with SLE) the Anti-dsDNA-NcX ELISA clearly demonstrated its superiority over the Anti-dsDNA RIA (Farr assay), showing an 8% higher sensitivity.

The Anti-dsDNS-NcX-ELISA can be performed manually or fully automatically (EUROIMMUN Analyzer I). Other competent test systems such as the Farr assay and the indirect immunofluorescence test (substrate Crithidia luciliae) continue to be of importance in the clarification of discrepant serological and clinical results.