IntroductionIn the present study, we analysed in detail nuclear autoantibodies and their associations in systemic sclerosis (SSc) patients included in the German Network for Systemic Scleroderma Registry.MethodsSera of 863 patients were analysed according to a standardised protocol including immunofluorescence, immunoprecipitation, line immunoassay and immunodiffusion.ResultsAntinuclear antibodies (ANA) were detected in 94.2% of patients. In 81.6%, at least one of the autoantibodies highly associated with SSc or with overlap syndromes with scleroderma features was detected, that is, anti-centromere (35.9%) or anti-topoisomerase I (30.1%), followed in markedly lower frequency by antibodies to PM-Scl (4.9%), U1-ribonucleoprotein (U1-RNP) (4.8%), RNA polymerases (RNAPs) (3.8%), fibrillarin (1.4%), Ku (1.2%), aminoacyl-transfer RNA synthetases (0.5%), To (0.2%) and U11-RNP (0.1%). We found that the simultaneous presence of SSc-associated autoantibodies was rare (1.6%). Furthermore, additional autoantibodies were detected in 55.4% of the patients with SSc, of which anti-Ro/anti-La, anti-mitochondrial and anti-p25/p23 antibodies were most frequent. The coexistence of SSc-associated and other autoantibodies was common (43% of patients). SSc-associated autoantibodies disclosed characteristic associations with clinical features of patients, some of which were previously not acknowledged.ConclusionsThis study shows that five autoantigens (that is, centromere, topoisomerase I, PM-Scl, U1-RNP and RNAP) detected more than 95% of the known SSc-associated antibody responses in ANA-positive SSc patients and characterise around 79% of all SSc patients in a central European cohort. These data confirm and extend previous data underlining the central role of the determination of ANAs in defining the diagnosis, subset allocation and prognosis of SSc patients.

Patients selected for the presence of sclerodermarelated antibodies (anti-DNA-topoisomerase I [antitop0 I; n = 431, anticentromere antibody [ACA; n = 631, or anti-Pm-Scl [n = 121) were studied for class I and class I1 major histocompatibility complex antigens, as well as for Gm and Km allotypes.

The detection of autoantibodies is an important element in the diagnosis and monitoring of disease progression in patients with autoimmune diseases. In laboratory diagnostic tests for connective tissue and autoimmune liver diseases, indirect immunofluorescence on HEp-2 cells plays a central role in a multistage diagnostic process. Despite the high quality of diagnostics, findings at different laboratories can differ considerably due to a lack of standardization, as well as subjective factors. The present paper formulates recommendations for the standardized processing and interpretation of the HEp-2 cell test for the detection of non-organ-specific (especially antinuclear) antibodies. It provides requirements regarding the diagnostic tests used, instructions for laboratory procedure and evaluation, and recommendations for interpretation. For an optimal laboratory diagnostic process, it is useful to have an informative, tentative clinical diagnosis and an experienced laboratory diagnostician. In addition, the following key elements are recommended: initial screening using indirect immunofluorescence on carefully chosen HEp-2 cells beginning with a serum dilution of 1:80 and evaluation under a microscope with powerful illumination; results from a titer of 1:160 upwards being considered positive; internal laboratory quality control; and standardized interpretation. The aim is to improve diagnostic tests and care of patients with autoimmune diseases as a central concern of the European Autoimmunity Standardization Initiative (EASI).

Background: Antibodies targeting DNA topoisomerase I (ATA) or centromere proteins (ACA) are associated with clinical subsets of patients with systemic sclerosis (SSc). The occurrence of those autoantibodies is considered to be mutually exclusive. Objective: To describe the clinical and immunogenetic data of three patients who are co-expressing both antibodies, and then review previous publications. Methods: Both antibodies were detected by different methods, including indirect immunofluorescence technique, enzyme linked immunosorbent assay, immunodiffusion, and immunoblot. Patients were HLA typed by serological and molecular genetic methods. Data were extracted from published reports for comparison. The search for published studies was through Medline and other database research programmes. Results: During routine laboratory diagnostics over several years three patients with scleroderma and coincidence of ATA and ACA were identified: patient 1 with diffuse SSc, Raynaud's phenomenon, puffy fingers and fingertip necrosis, contractures, and calcinosis; patient 2 with diffuse SSc, Raynaud's phenomenon, oedema of the hands, and interstitial calcinosis of hands, knees, and shoulders, and pulmonary fibrosis; patient 3 with scleroderma of hands, forearms, and face, Raynaud's phenomenon, puffy fingers, finger contractures, fingertip necrosis, and calcinosis. All three patients studied were carriers of HLA alleles known to be associated with these autoantibodies. In serial measurements the concentrations of the two antibodies showed independent or even reverse fluctuations. Screening of 100 patients with ACA for ATA and vice versa disclosed no further patients with coincidence of these antibodies. Twenty eight cases of ACA/ATA coexistence in 5423 patients (0.52%) with SSc or SSc associated symptoms were found in an analysis of published studies. Conclusion: The expression of ATA and ACA is not totally mutually exclusive, but coincidence is rare (<1% of patients with SSc). Patients with both autoantibodies often have diffuse scleroderma and show immunogenetic features of both antibody defined subsets of SSc.