Department of Neurology, Friedrich-Baur-Institute, Ludwig-Maximilians-University Munich, Ziemssenstr. 1a, 80336, Munich, Germany.
Institute of Laboratory Medicine, University Hospital, LMU Munich, Munich, Germany.
J Neurol. 2019 Jun;266(6):1358-1366. doi: 10.1007/s00415-019-09266-4. Epub 2019 Mar 6.
Myositis-associated antibodies (MAA) and myositis-specific antibodies (MSA) are detected in patients with idiopathic inflammatory myopathies (IIM); their role as diagnostic biomarkers is however still debated. The aim of our study was to assess the utility of MAA/MSA assessed by new line immunoassays in detecting myositis among neuromuscular patients.
We retrospectively analysed sera samples obtained from patients tested for myositis antibodies with the "Euroline: Autoimmune Inflammatory Myopathies 16Ag" and "myositis profile 3" kits (Mi-2, TIF1γ, MDA5, NXP2, SAE1, Jo-1, SRP, PL-7/12, EJ, OJ, Ro-52, Ku, PM-Scl75/100). First symptom, CK, EMG, muscle biopsy and diagnosis were also analysed. Using logistic regression analysis, two diagnostic models were built to evaluate the diagnostic power of MAA/MSA in distinguishing myositis patients from controls and other myopathies.
1229 patients were identified. 141 patients had a bioptic confirmed IIM; other diagnoses included: myopathy (n = 357), other neuromuscular diseases (n = 144) and no neuromuscular diseases (n = 587). The specificity was 95% for MSA and 89% for MAA, the sensitivity 20% and 22%, respectively. MAA showed no use in differentiating myositis patients from controls, whereas MSA had limited effect (OR = 5.165), compared to other variables as EMG (OR = 47.755) or CK > 2000 U/L (OR = 45.307). MSA were, however, the most useful parameter differentiating IIM from non-IIM patients (OR = 7.259), better than CK > 2000 U/L (OR = 4.033) and MAA (OR = 2.737).
Line immunoassays for myositis antibodies show high specificity but low sensitivity. Their usefulness as diagnostic biomarkers widely depends on the clinical settings. Our study suggests that MSA/MAA should be used for confirmatory and differential diagnosis rather than for screening purposes in inflammatory myopathies.
肌炎相关抗体（MAA）和肌炎特异性抗体（MSA）可在特发性炎性肌病（IIM）患者中检测到；然而，它们作为诊断生物标志物的作用仍存在争议。我们研究的目的是评估通过新的线免疫分析检测肌炎抗体在神经肌肉患者中检测肌炎的效用。
我们回顾性分析了用“Euroline：自身免疫性炎性肌病 16Ag”和“肌炎谱 3”试剂盒（Mi-2、TIF1γ、MDA5、NXP2、SAE1、Jo-1、SRP、PL-7/12、EJ、OJ、Ro-52、Ku、PM-Scl75/100）检测肌炎抗体的患者的血清样本。还分析了首发症状、肌酸激酶（CK）、肌电图（EMG）、肌肉活检和诊断。使用逻辑回归分析，建立了两个诊断模型，以评估 MAA/MSA 在区分肌炎患者与对照组和其他肌病患者方面的诊断能力。
共确定了 1229 名患者。141 名患者经活检证实为 IIM；其他诊断包括：肌病（n=357）、其他神经肌肉疾病（n=144）和无神经肌肉疾病（n=587）。MSA 的特异性为 95%，MAA 的特异性为 89%，敏感性分别为 20%和 22%。MAA 对区分肌炎患者与对照组无作用，而 MSA 的作用有限（OR=5.165），与 EMG （OR=47.755）或 CK>2000 U/L （OR=45.307）等其他变量相比。然而，MSA 是区分 IIM 与非 IIM 患者最有用的参数（OR=7.259），优于 CK>2000 U/L（OR=4.033）和 MAA（OR=2.737）。
肌炎抗体的线免疫分析具有高特异性但低敏感性。其作为诊断生物标志物的有效性在很大程度上取决于临床环境。我们的研究表明，MSA/MAA 应用于确认和鉴别诊断，而不是用于炎症性肌病的筛查目的。
