Comparison of different immunoassays detecting anti-chromatin autoantibodies in systemic lupus erythematosus (SLE)

Introduction

Anti-double-strand DNA (dsDNA) autoantibodies are considered a hallmark of SLE and many assays have been developed to improve the determination of these antibodies. Recently, autoantibodies to nucleosome, the fundamental unit of chromatin, have been shown to constitute a new and very specific marker of SLE.

Methods

To evaluate the diagnostic value of (A) Crithidia lucillae indirect immunofluorescence (CLIFT), anti-dsDNA immunoassays using (B) purified dsDNA (Quanta LiteTM dsDNA ELISA INOVA, San Diego, CA), (C) recombinant plasmid dsDNA (EliATM, Pharmacia, Freiburg, Germany) and (D) anti-nucleosome immunoassay (Quanta Lite Chromatin ELISATM, INOVA, San Diego, CA), we investigated in a prospective study all the sera sent to our laboratory for anti-dsDNA detection during 2 months. 122 sera were enrolled in this study of which 16 appear to be from SLE patients and we assessed the sensitivity and specificity of the assays. We also compared a group of 30 SLE patients with other autoimmune diseases (19 cutaneous lupus, 22 Sjögren's syndrome, 14 systemic scleroderma) in a retrospective study.

Results

In the prospective study, the sensitivity for SLE was 13%, 53%, 47% and 60% for test A, B, C and D, respectively; the specificity was 99%, 94%, 94% and 99% for test A, B, C and D, respectively. Results were similar in the retrospective study.

Conclusion

Anti-nucleosome autoantibodies are sensitive and specific markers for SLE. However, other studies are necessary to evaluate if they are also useful in monitoring disease activity.