Background Systemic sclerosis (SSc) is a rare connective tissue disorder, which leads to progressive fibrosis of many organs. Its course is characterised by the presence of two classical autoantibodies: anti-topoisomerase I (ATA, Scl-70) and anti-centromere (ACA). In recent years, the presence of antibodies against a wider range of antigens was demonstrated, namely: RNA polymerase III, Fibrillarin, NOR90, Th/To, PM-Scl-100, PM-Scl-75, Ku, PDGFR, but their clinical significance is relatively little known.
Objectives To evaluate the prevalence of selected autoantibodies in the population of Polish patients with systemic sclerosis and to examine associations between their presence and selected clinical signs and symptoms of the disease. A secondary objective was to compare the sensitivity of the two line immunoblot assays: ANA Profile 3 and Systemic Sclerosis Profile.
Methods The study was prospective and cross-sectional in design. The study group consisted of 75 patients. Sera of patients diagnosed with systemic sclerosis (ACR criteria) were secured and assessed for the presence of antibodies by indirect immunofluorescence (HEp-2 and monkey liver) and line immunoblot assays (LIAs): ANA Profile 3 and Systemic Sclerosis Profile by EUROIMMUN (Germany). The organ involvement was evaluated in accordance with the Minimal Essential Data Set used by EUSTAR. The results were subject to statistical analysis using the Fisher exact and McNemara Chi-square tests and p<0.05 was considered to be statistically significant.
Results In the population studied the following prevalence of autoantibodies against antigens was observed: Scl-70 (40.0%), Ro -52 (25.3%), PM-Scl-75 (20.0%), CENP-B (18.7%), CENP-A (16.0%), PM-Scl-100 (14.7%), Fibrillarin (9.3%), Th/To (9.3%), RNA polymerase III 11 kDa (5.3%), PDGFR (4.0%), NOR-90 (2.7%), RNA polymerase III 155 kDa (2.7%), Ku (1.3%). Significant associations between the presence of autoantibodies and organ involvement were found: ATA (dcSSc > lcSSc, rare muscle atrophy), Ro -52 (rare stomach symptoms), CENP-B and A (lcSSc > dcSSc), PM-Scl-100 and 75 (PM/SSc overlap, CK increase, muscle weakness, muscle atrophy and interstitial lung disease, PM-Scl-100 (dcSSc and dyspnea of NYHA ≥ II), Fibrillarin (muscle atrophy, proteinuria, conduction abnormalities in the heart), Th/To (proteinuria, arthritis and muscle weakness), RNA Polymerase III 11 kDa (systemic hypertension), RNA polymerase III 155 kDa (scleroderma renal crisis), PDGFR (dcSSc). In addition, Systemic Sclerosis Profile was significantly more sensitive in detecting SSc-related autoantibodies than ANA Profile 3 (sensitivity: 80.0% and 68.0% respectively, McNemar's Chi-square p=0.008).
Conclusions Assessment of autoantibodies in systemic sclerosis allows identification of serological subgroups of patients with a specific clinical course and improves the sensitivity of serological diagnosis.
Acknowledgements We are greatly indebted to the clinical and laboratory staff of the Department of Rheumatology and Internal Medicine for help with patient recruitment and conducting serological tests.
Disclosure of Interest None declared