Systemic sclerosis (SSc) is a heterogeneous autoimmune disease associated with several anti-nuclear antibodies (ANA), including those in the classification criteria (anti-centromere, anti-topoisomerase I (Scl-70), anti-RNA Pol III). However, the presence of less common antibodies such as anti-fibrillarin (U3-RNP) that generate a clumpy nucleolar pattern by HEp-2 indirect immunofluorescence assay (IFA, ICAP AC-9) are considered disease specific and are with clinical subsets of SSc, therefore playing a role in diagnosis and prognosis. A specific and sensitive anti-fibrillarin assay would be an important addition to serological diagnosis and evaluation of SSc. The goal of this study was to evaluate a new particle-based multi-analyte technology (PMAT) for the measurement of anti-fibrillarin antibodies. A total of 149 patient samples were collected including 47 samples from France (Lyon and Paris, n = 32) and Italy (Careggi Hospital, Florence, n = 15) selected based on AC-9 HEp-2 IFA staining (> 1:640, clumpy nucleolar pattern) and 102 non-SSc controls (inflammatory bowel disease (IBD) n = 20, Sjögren’s syndrome (SjS) n = 20, infectious disease (ID) n = 7, systemic lupus erythematosus (SLE) n = 17, rheumatoid arthritis (RA) n = 17, and healthy individuals (HI) n = 21). All samples were tested on the anti-fibrillarin PMAT assay (research use only, Inova Diagnostics, USA). Additionally, the 47 anti-fibrillarin positive samples were also tested on PMAT assays for detecting other autoantibodies in ANA-associated rheumatic diseases (AARD). Anti-fibrillarin antibody data performed by fluorescence enzyme immunoassay (FEIA, Thermo Fisher, Germany) was available for 34 samples. The anti-fibrillarin PMAT assay was positive in 31/32 (96.9%, France) and 12/15 (80.0%, Italy) of samples preselected based on the AC-9 IIF pattern (difference p = 0.09). Collectively, the PMAT assay showed 91.5% (95% confidence interval (CI): 80.1–96.6%) sensitivity with 100.0% (95% CI: 96.4–100.0%) specificity in non-SSc controls. Strong agreement was found between PMAT and FEIA with 100.0% positive qualitative agreement (34/34) and quantitative agreement (Spearman’s rho = 0.89, 95% CI: 0.77.9–0.95%, p < 0.0001). Although most anti-fibrillarin positive samples were mono-specific (69.8%), some expressed additional antibodies (namely Scl-70, centromere, dsDNA, Ro52, Ro60, SS-B, Ribo-P, DFS70, and EJ). In conclusion, this first study on anti-fibrillarin antibodies measured using a novel PMAT assay shows promising results where the new PMAT assay had high level of agreement to FEIA for the detection of anti-fibrillarin antibodies. The availability of novel AFA assays such as PMAT might facilitate the clinical deployment, additional studies, standardization efforts, and potentially consideration of AFA for next generations of the classification criteria.

系统性硬化症 (SSc) 是一种异质性自身免疫性疾病，与多种抗核抗体 (ANA) 相关，包括分类标准中的抗体（抗着丝粒抗体、抗拓扑异构酶 I (Scl-70) 抗体、抗 RNA Pol III 抗体）。然而，一些不太常见的抗体，如抗原纤维蛋白 (U3-RNP)，通过 HEp-2 间接免疫荧光测定（IFA、ICAP AC-9）产生块状核仁图案，被认为是疾病特异性的，并且与 SSc 的临床亚型有关，因此在诊断和预后中发挥作用。特异性且灵敏的抗原纤维蛋白测定将是 SSc 血清学诊断和评估的重要补充。本研究的目的是评估一种用于测量抗原纤维蛋白抗体的新型基于颗粒的多分析物技术 (PMAT)。总共收集了 149 名患者样本，其中 47 份来自法国（里昂和巴黎，n  = 32）和意大利（佛罗伦萨 Careggi 医院，n  = 15），根据 AC-9 HEp-2 IFA 染色（> 1:640）选择，块状核仁模式）和 102 个非 SSc 对照（炎症性肠病 (IBD) n  = 20，干燥综合征 (SjS) n  = 20，传染病 (ID) n  = 7，系统性红斑狼疮 (SLE) n  = 17，类风湿性关节炎 (RA) n  = 17，健康个体 (HI) n  = 21)。所有样品均经过抗原纤维蛋白 PMAT 检测（仅供研究使用，美国 Inova Diagnostics）。此外，还对 47 个抗原纤维蛋白阳性样本进行了 PMAT 检测，以检测 ANA 相关风湿病 (AARD) 中的其他自身抗体。通过荧光酶免疫分析（FEIA，Thermo Fisher，德国）获得了 34 个样品的抗原纤维蛋白抗体数据。根据 AC-9 IIF 模式预选的样本中，31/32（96.9%，法国）和 12/15（80.0%，意大利）的抗原纤维蛋白 PMAT 检测呈阳性（差异p  = 0.09）。总的来说，PMAT 检测在非 SSc 对照中显示出 91.5%（95% 置信区间 (CI)：80.1–96.6%）的敏感性和 100.0%（95% CI：96.4–100.0%）的特异性。PMAT 和 FEIA 之间存在很强的一致性，具有 100.0% 的定性一致性 (34/34) 和定量一致性（Spearman's rho = 0.89，95% CI：0.77.9–0.95%，p < 0.0001)。尽管大多数抗原纤维蛋白阳性样本是单特异性的（69.8%），但有些样本表达额外的抗体（即 Scl-70、着丝粒、dsDNA、Ro52、Ro60、SS-B、Ribo-P、DFS70 和 EJ）。总之，这项关于使用新型 PMAT 测定测量的抗原纤维蛋白抗体的首次研究显示了有希望的结果，其中新的 PMAT 测定与 FEIA 在检测抗原纤维蛋白抗体方面高度一致。新型 AFA 检测（例如 PMAT）的可用性可能会促进临床部署、额外研究、标准化工作，并有可能考虑将 AFA 作为下一代分类标准。