Anti-dsDNA-NcX ELISA: dsDNA-loaded nucleosomes improve diagnosis and monitoring of disease activity in systemic lupus erythematosus

Abstract

IntroductionThe objective of this study was to compare the clinical usefulness of the new anti-double-stranded DNA nucleosome-complexed enzyme-linked immunosorbent assay (Anti-dsDNA-NcX ELISA), which is based on dsDNA-loaded nucleosomes as antigens, with established test systems based on dsDNA or nucleosomes alone for systemic lupus erythematosus (SLE) diagnostics and determination of disease activity.MethodsSera from a cohort of 964 individuals comprising 207 SLE patients, 357 disease controls and 400 healthy donors were investigated using the Anti-dsDNA-NcX ELISA, Farr assay, Anti-dsDNA ELISA, Anti-nucleosome ELISA and Crithidia luciliae immunofluorescence (CLIF) assay, all of which are tests available from EUROIMMUN Medizinische Labordiagnostika AG (Lübeck, Germany). Receiver operating characteristic curve analyses were performed to compare the sensitivity and specificity of each assay. The test results yielded by these assays in a group of 165 fully characterized SLE patients were compared with the corresponding medical records.ResultsThe Anti-dsDNA-NcX ELISA was found to have a sensitivity of 60.9% and a specificity of 98.9% in all 964 individuals at the manufacturer's cutoff of 100 U/ml. At a comparable specificity of 99%, the sensitivity amounted to 59.9% for the Anti-dsDNA-NcX ELISA, 54.1% for the Farr assay, 53.6% for the antinucleosome ELISA and 35.8% for the anti-dsDNA ELISA. The CLIF assay had a sensitivity of 28.0% and a specificity of 98.2%. The Anti-dsDNA-NcX ELISA correlated mostly with global disease activity in a cross-sectional analysis. In a longitudinal analysis of 20 patients with 69 patient visits, changes in Anti-dsDNA-NcX ELISA and antinucleosome ELISA results correlated highly with changes in disease activity over time.ConclusionsThe use of dsDNA-complexed nucleosomes as antigens in ELISA leads to optimized determination of diagnosis and disease activity in SLE patients and is available for clinical practice.

IFNα and its response proteins, IP-10 and SIGLEC-1, are biomarkers of disease activity in systemic lupus erythematosus

“…Erythrocyte-bound C3 and C4 reflect DA cross-sectionally and longitudinally nearly as well as serum levels of complement C3 and C4 6. We and others have found that antibodies against nucleosomes7 8 and dsDNA-complexed nucleosomes (Anti-dsDNA-NcX ELISA) may be more useful for monitoring DA than traditional anti-dsDNA antibodies 9…”

Autoantibodies, complement and type I interferon as biomarkers for personalized medicine in SLE

“…12,13 The most commonly used marker autoantibodies in SLE react with dsDNA, Smith (Sm) antigen, nucleosomes and ribosomal P proteins. 14,15 Antinucleosome antibodies occur in SLE at a frequency of 60%-100 %. 16 The frequency range may be influenced by factors like ethnicity, disease duration, disease activity and treatment.…”

“…17 Interestingly, ELISAs using the strong adhesive property of nucleosomes (instead of commonly used linkers like methylated albumin, protamine sulfate or poly-L-lysine) to attach dsDNA to the plate, showed even higher diagnostic performance in SLE, and outperformed even the Farr assay. 14 …”

Comparison of three ELISA methods with CLIF test for detection of Anti-dsDNA antibody

“…Bu testler arasında duyarlılık ve özgüllük açısından büyük farklar mevcuttur ve özellikle de antidsDNA ELISA'nın farklı ticari kitleri arasında bu fark belirgindir (11). ELISA testi ile çalışılan anti-dsDNA sonuçları IgG spesifik CLIF veya Farr RIA yöntemleri ile doğrulanmalıdır (12,13 …”