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Open Access Highly Accessed Research article

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

Robert Biesen1, Cornelia Dähnrich2, Anke Rosemann2, Fidan Barkhudarova1, Thomas Rose1, Olga Jakob1, Anne Bruns1, Marina Backhaus1, Winfried Stöcker2, Gerd-Rüdiger Burmester1, Wolfgang Schlumberger2, Karl Egerer1 and Falk Hiepe1*

Author Affiliations

1 Department of Rheumatology and Clinical Immunology, Charité Universitätsmedizin Berlin, Chariteplatz 1, Berlin D-10117, Germany

2 EUROIMMUN Medizinische Labordiagnostika AG, Seekamp 31, Lübeck D-23560, Germany

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Arthritis Research & Therapy 2011, 13:R26  doi:10.1186/ar3250

Published: 10 February 2011

Abstract

Introduction

The 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.

Methods

Sera 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.

Results

The 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.

Conclusions

The 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.