Department of Rheumatology and Immunology, West China Hospital, Sichuan University, Chengdu, Sichuan, China.
Department of Rheumatology, The First People's Hospital of Shuangliu District, West China Airport Hospital of Sichuan University, Chengdu, Sichuan, China.
Rheumatology (Oxford). 2023 Nov 2;62(11):3742-3748. doi: 10.1093/rheumatology/kead109.
N-terminal fragment of titin (N-titin) is a marker of sarcomere damage in striated muscles; however, its value in patients with IIM (idiopathic inflammatory myopathy) is unclear. This study aimed to investigate the diagnostic value of N-titin for skeletal muscle damage in patients with IIM.
Urine samples from 62 patients with IIM, 59 patients with other CTD diseases, and 29 healthy controls were collected to detect N-titin by ELISA assays. Clinical features and laboratory data were all included in logistic regression analysis to obtain the independent predictive factor for skeletal muscle damage.
Urinary N-titin level of the IIM group [168.3 (19.0, 1279.0) pmol/mg cr] was significantly higher than that in CTD controls [2.80 (1.53, 3.60)] and healthy controls [1.83 (1.09, 2.95)] (P < 0.001). IIM patients with skeletal muscle injury had a significantly higher level of urinary N-titin [1001.0, (181.8, 1977.0)] than those without [9.3, (5.8, 23.9)] (P < 0.001). The N-titin level was strongly correlated with CK (r = 0.907, P < 0.001) and muscle disease activity assessment scores by Spearman correlation analysis. After adjusting for the anti-MDA5 antibody and cardiac troponin T, N-titin was shown to independently predict skeletal muscle damage in patients with IIM (odds ratio = 1.035, 95% CI: 1.002, 1.069, P = 0.039). The cut-off value of urinary N-titin to diagnose skeletal muscle damage was 89.9 pmol/mg Cr, with a sensitivity of 87.8% and a specificity of 100% (AUC = 0.971, 95% CI: 0.938, 1.000, P < 0.001).
Urinary N-titin is a non-invasive and independent predictive factor for determining skeletal muscle damage in patients with IIM.
肌联蛋白 N 端片段（N-titin）是横纹肌肌节损伤的标志物；然而，其在特发性炎性肌病（IIM）患者中的价值尚不清楚。本研究旨在探讨 N-titin 对 IIM 患者骨骼肌损伤的诊断价值。
收集 62 例 IIM 患者、59 例其他 CTD 疾病患者和 29 名健康对照者的尿样，通过 ELISA 法检测 N-titin。将临床特征和实验室数据均纳入逻辑回归分析，以获得骨骼肌损伤的独立预测因素。
IIM 组尿 N-titin 水平[168.3（19.0，1279.0）pmol/mg cr]明显高于 CTD 对照组[2.80（1.53，3.60）]和健康对照组[1.83（1.09，2.95）]（P<0.001）。有骨骼肌损伤的 IIM 患者尿 N-titin 水平[1001.0，（181.8，1977.0）]显著高于无骨骼肌损伤的患者[9.3，（5.8，23.9）]（P<0.001）。N-titin 水平与 CK 呈强相关（r=0.907，P<0.001），Spearman 相关性分析显示与肌病活动评估评分也呈强相关。校正抗 MDA5 抗体和肌钙蛋白 T 后，N-titin 可独立预测 IIM 患者的骨骼肌损伤（比值比=1.035，95%CI：1.002，1.069，P=0.039）。尿 N-titin 诊断骨骼肌损伤的截断值为 89.9 pmol/mg cr，灵敏度为 87.8%，特异性为 100%（AUC=0.971，95%CI：0.938，1.000，P<0.001）。
尿 N-titin 是一种非侵入性的独立预测因子，可用于确定 IIM 患者的骨骼肌损伤。
