Reactive arthritis (ReA) is a member of seronegative spondyloarthropathy (SSA), which involves an acute/subacute onset of asymmetrical lower limb joint inflammation weeks after a genitourinary/gastrointestinal infection. The diagnosis is clinical because it is difficult to culture the microbes from synovial fluid. Arthritis patients with a similar clinical picture but lapsed history of an immediate preceding infection that do not fulfill the diagnostic criteria of other members of SSA, such as ankylosing spondylitis, psoriatic arthritis, and arthritis associated with inflammatory bowel disease, are labeled as peripheral undifferentiated spondyloarthropathy (uSpA). Both ReA and uSpA patients show a strong association with class I major histocompatibility complex allele, HLA-B27, and a clear association with an infectious trigger; however, the disease mechanism is far from clear. Because the clinical picture is largely dominated by rheumatoid-arthritis (RA)-like features including elevated levels of inflammatory markers (such as ESR, CRP, etc.), these overlapping symptoms often confound the clinical diagnosis and represent a clinical dilemma, making treatment choice more generalized. Therefore, there is a compelling need to identify biomarkers that can support the diagnosis of ReA/uSpA. In the present study, we performed NMR-based serum metabolomics analysis and demonstrated that ReA/uSpA patients are clearly distinguishable from controls and further that these patients can also be distinguished from the RA patients based on the metabolic profiles, with high sensitivity and specificity. The discriminatory metabolites were further subjected to area under receiver operating characteristic curve analysis, which led to the identification of four metabolic entities (i.e., valine, leucine, arginine/lysine, and phenylalanine) that could differentiate ReA/uSpA from RA.

中文翻译：

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与风湿性关节炎相比，基于NMR的血清代谢组学揭示了反应性关节炎的独特代谢模式。

反应性关节炎（ReA）是血清阴性脊椎关节病（SSA）的成员，它涉及泌尿生殖系统/胃肠道感染几周后，不对称下肢关节炎症的急性/亚急性发作。诊断是临床的，因为很难从滑液中培养出微生物。具有类似临床症状但已过前感染史且未满足SSA其他成员诊断标准的关节炎患者，如强直性脊柱炎，银屑病关节炎和与炎症性肠病相关的关节炎，被标记为周围性未分化脊椎关节病（uSpA）。ReA和uSpA患者均显示出与I类主要组织相容性复杂等位基因HLA-B27的强相关性，并且与感染触发因素有明显的相关性。然而，该病的机制尚不清楚。因为临床表现主要由类风湿关节炎（RA）样特征所主导，包括炎症标志物（例如ESR，CRP等）水平升高，所以这些重叠的症状常常使临床诊断感到困惑，并代表了临床难题，因此进行了治疗选择比较笼统。因此，迫切需要鉴定可以支持ReA / uSpA诊断的生物标志物。在本研究中，我们进行了基于NMR的血清代谢组学分析，并证明ReA / uSpA患者与对照组明显不同，并且基于代谢谱，这些患者也可以与RA患者区分开，具有高度的敏感性和特异性。