ACA = anti-centromere antibodies; AMA = antimitochondrial antibodies; ATA = anti-topoisomerase I antibodies;; RNAP = RNA polymerase; RNP = ribonucleoprotein. From 213 patients, more than one serum sample was available (from 2 to 25 samples). 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, Cefradine 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. Conclusions This 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 Cefradine the central role of the determination of ANAs in defining the diagnosis, subset allocation and prognosis of SSc patients. strong class=”kwd-title” Keywords: systemic sclerosis, scleroderma, autoantibodies, antinuclear antibodies Introduction Autoantibodies targeting characteristic nuclear antigens are one of the hallmarks of systemic sclerosis (SSc) [1-3]. The occurrence of different antinuclear antibodies (ANAs) is associated with distinct disease subtypes and with differences in disease severity, including extent of skin involvement, internal organ manifestation and prognosis. Although the current SSc criteria of the American College of Rheumatology  do not include the presence of ANAs, The detection of scleroderma-associated antibodies may be a valuable tool in the diagnosis of patients with very early SSc or only subtle symptoms [5,6]. For instance, in a recent study of patients with Raynaud’s phenomenon, the presence of ANAs (adjusted HR = 5.67) and SSc-associated antibodies (HR = 4.7) was the strongest independent predictor of definite SSc . Some of the autoantibodies in SSc are regarded as disease-specific and can be correlated with genetic, demographic, diagnostic, clinical and prognostic aspects of the disease [1,3]. Therefore, autoantibodies are pivotal tools in the diagnosis of Cefradine SSc by helping clinicians make decisions whether to perform further, more detailed and efficient diagnostic procedures, as well as decisions addressing disease management. For frequently occurring antibodies such as anti-centromere (ACA) and anti-topoisomerase I (ATA), reliable detection systems based on ELISA or other binding tests have been developed. Other antibodies (that is, to fibrillarin, RNA polymerases (RNAPs) and so on) are not identified by common test procedures, but rather by laboratories able to perform sophisticated procedures to confirm the results on the basis of more than one independent method. Even for the most common autoantibodies, the choice of the detection method used is critical to the sensitivity and specificity of the results and hence their diagnostic value . Researchers in numerous studies have examined the presence of antibodies to single predefined antigens in SSc and their clinical associations, whereas many of the investigators who have comprehensively examined large SSc patient cohorts have often restricted their autoantibody analyses to the most common SSc Cefradine antibodies, ACA and ATA [8-12], or analysed only a few additional antibodies [13-17]. The aim of this study was therefore to characterise all known non-organ-specific, SSc-associated autoantibodies, as well as other, potentially new nuclear autoantibodies by using a standardised protocol in the large SSc patient cohort included in the German Network for Systemic Scleroderma Registry, and to correlate these findings with the clinical characteristics of these patients. Materials and methods Patients Serum samples from 863 consecutive patients included in the German Network for Systemic Scleroderma Registry between 2004 and 2007 from 23 different clinical centres were analysed. Patient data are gathered and registered using a consensual registration form and reference documents with item definitions and recommendations for organ-specific diagnostic procedures as previously described [18,19]. Of the patients included, 82.9% were female, their mean age SD was 58.0 13.4 years (median = 60 years, range 12 to 93). The patients’ age at disease onset ranged from ZAP70 3 to 87 years (median = 49 years, mean = 47.7 14.2). The registry defines five subsets, that is, limited cutaneous and diffuse cutaneous SSc , overlap syndrome [21,22], systemic sclerosis sine scleroderma [23,24] and undifferentiated connective tissue disease with features of scleroderma [25,26], as recently described . The latter subset corresponds largely to the subgroup ‘early SSc’ as described by LeRoy and.