This study aimed to classify the distinct group of patients with axial spondyloarthritis (SpA) on tumour necrosis factor alpha inhibitors (TNFi) according to the baseline characteristics using a clustering algorithm. The clinical characteristics and demographic data of patients with axial SpA included in the Korean College of Rheumatology Biologics and Targeted Therapy registry were investigated. The patterns of disease manifestations were examined using divisive hierarchical cluster analysis. After clustering, we compared the clinical characteristics of patients and the drug survival of TNFi between the classified groups. A total of 1042 patients were analysed. The cluster analysis classified patients into two groups: axial group predominantly showing isolated axial manifestations (n = 828) and extra-axial group more frequently showing extra-axial symptoms (n = 214). Almost all extra-axial symptoms (peripheral arthritis, enthesitis, uveitis, and psoriasis) were more frequently observed in the extra-axial group than in the axial group. Moreover, patients in the extra-axial group had shorter disease duration, later disease onset, and higher disease activity than those in the axial group. The disease activity was comparable between the two groups after 1 year of treatment with TNFi. Interestingly, the extra-axial group had a lower drug survival with TNFi than the axial group (p = 0.001). Cluster analysis of patients with axial SpA using TNFi classified two distinct clinical phenotypes. These clusters had different TNFi drug survival, clinical characteristics, and disease activity.

中文翻译：

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基于临床特征的使用肿瘤坏死因子α抑制剂的中轴型脊柱关节炎患者的聚类分析

本研究旨在使用聚类算法根据基线特征对使用肿瘤坏死因子 α 抑制剂 (TNFi) 的轴型脊柱关节炎 (SpA) 患者进行分类。研究了韩国风湿病学生物制剂和靶向治疗登记处中轴性 SpA 患者的临床特征和人口统计数据。使用分裂层次聚类分析检查疾病表现的模式。聚类后​​，我们比较了分类组之间患者的临床特征和 TNFi 的药物存活率。共分析了 1042 名患者。聚类分析将患者分为两组：轴组主要表现出孤立的轴表现（n = 828），轴外组更频繁地表现出轴外症状（n = 214）。与轴组相比，轴外组几乎所有轴外症状（外周关节炎、肌腱端炎、葡萄膜炎和银屑病）都更常见。此外，与中轴组相比，轴外组患者的病程较短、发病较晚、疾病活动度较高。用 TNFi 治疗 1 年后，两组的疾病活动度具有可比性。有趣的是，轴外组的 TNFi 药物存活率低于轴组（p = 0.001）。使用 TNFi 对轴向 SpA 患者进行聚类分析，将其分为两种不同的临床表型。这些集群具有不同的 TNFi 药物存活率、临床特征、