AB1197 Multiparametric analysis of connective tissue disease specific autoantibodies using a spot immunoassay (SERASPOT®ANA)

Background Because autoantibody profiling compared to single autoantibody determination is more relevant for diagnostics, differential diagnostics and even prognostics of the different kinds of connective tissue diseases (CTD), cost and time saving multiplex assays are more and more used in routine practice.1 Objectives Evaluation of the diagnostic relevance of the SeraSpot® ANA assay (Seramun Diagnostica GmbH, Heidesee, Germany), a novel spot immunoassay for multiplex analysis of the main connective tissue disease (CTD) specific autoantibodies (AABs) against dsDNA, histone, nucleosome, Scl-70, U1-RNP, Sm, PCNA, RibP, Ro52/TRIM21, Ro60, La/SS-B, CENP-B, Jo-1, PM/Scl-100, and Ku) based on autoantigens immobilised in microtiter plates. Methods AAB profiles using the SeraSpot® ANA assay were determined in sera of 381 patients with CTD and 202 apparently healthy individuals (AHI). The CTD patients comprises 105 SLE, 117 systemic sclerosis (SSc), 32 Sjogren’s syndrome (SjS), 58 idiopathic inflammatory myopathies (IIM), 5 mixed connective tissue disease (MCTD), and 64 undifferentiated connective tissue disease patients (UCTD). Results At least one CTD associated AAB was positive in 88.2% of the tested CTD patients. A high diagnostic specificity for CTD above 95% compared to AHI were found for antibodies to dsDNA, RibP, Sm, Ro60, Ro52, CENP-B, Scl70, PM/Scl-100, Ku and Jo-1. Excluding low-titre reactivity, the specificity of U1-RNP, nucleosome, histone and La/SS-B antibodies was also very high (96.5%–98%) regarding CTD diagnosis. The highest specificities vs. AHI were found for anti-Sm, -Ro60, -RibP and -Jo1 antibodies (99.5%), followed by anti-CENP-B (99%), -dsDNA (98,5%), -Ku (98.5%) and -Ro52 antibodies (98%). Regarding SLE, 104 (99%) were positive for SLE-associated AABs. Anti-dsDNA antibodies were most frequently found (88.6%). The highest specificities (98.5%–99.5%) for SLE compared to AHI were found for anti-dsDNA, -RibP, -Sm, and -Ro60 antibodies. SjS relevant AABs against Ro60, Ro52 and La/SS-B were seen in 81.3%, 84.4% and 46.9% of the SjS patients, respectively. The diagnostic specificity of Ro60 antibodies for SLE and SjS compared to other SARD (excluding UCTD) is 96.8% and 99.5%–100% compared to AHI. SSc associated AAB against Scl-70, CENP-B, PM/Scl-100 and -U1-RNP were found in 53.0%, 20.5%, 8.6%, and 13.7% of the included SSc cases, respectively, with diagnostic specificities between 96% and 99%. AABs against Jo-1, PM/Scl-100, U1-RNP, Ro52 and Ku were positive with high specificity (98.4%–99.5%) in 29.3%, 10.3%, 19% (100% of MCTD), 27.6% and 10.3% of IIM patients, respectively. Conclusions In combination with the HEp-2 cell assay, the SeraSpot® ANA assay can be used as a novel cost-effective multiplex assay for the serological confirmation of CTDs. Reference [1] Mahler M, Meroni PL, Bossuyt X, Fritzler MJ. Current concepts and future directions for the assessment of autoantibodies to cellular antigens referred to as anti-nuclear antibodies. J Immunol Res2014; Article ID 315179, doi.org/10.1155/2014/315179 Disclosure of Interest None declared