AB0673 Testing for antibodies specific to fibrillarin (U3 RNP) shows added value for diagnosis of systemic sclerosis

Background Systemic sclerosis (SSc) is a heterogeneous and often systemic autoimmune disorder characterised by specific autoantibody subsets. The disease is associated with anti-nuclear antibodies (ANA) and the detection of each of the autoantibodies is useful during diagnosis. Most SSc patients are positive for anti-centromere or anti-Scl70 antibodies. The presence of more rare antibodies to, e.g. Fibrillarin (U3 RNP), RNA-polymerase III and PM-Scl are often indicative of a systemic or a limited skin involvement. Objectives In this in-house study the prevalence, and clinical sensitivity and /specificity of anti-Fibrillarin antibodies in a subset of patients diagnosed with SSc was investigated. The major aim was to find out whether Fibrillarin testing would identify patients which are negative for standard parameters and therefore add value forin the diagnosticis workup for patients with suspected SSc. Methods Sera from 187 SSc patients, 53 blood donors and 177 disease controls were analysed for the presence of antibodies to CENP, Scl-70s, PM-Scl, RNA Pol III and Fibrillarin using the EliA platform (Thermo Fisher Scientific, Freiburg, Germany). Results In 149 out of the 187 patients one or more of the tested parameters were detected. Fibrillarin was identified in 7 out of the 149 patients including 6 solely positive for Fibrillarin. Overall sensitivity within this study is 79,68% with an overall specificity of 92,17%; for Fibrillarin sensitivity of 3,74% and specificity of 98,70% was shown within this cohort. Conclusions Increased diagnostic sensitivity was shown in this cohort of 187 patients with SSc by adding the analysis of antibodies against Fibrillarin. Testing allowed additional identification of 6 SSc patients which correlates to an increase of 3,74% in sensitivity. References Arthritis Res Ther 2003, 5:80–93. Rheumatology 2001;40:1157–1162. Disclosure of Interest None declared