Department of Neuroscience, Università Cattolica del Sacro Cuore, Rome, Italy.
Department of Chemistry and Clinical Biochemistry, Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Rome, Italy.
Eur J Neurol. 2024 Dec;31(12):e16435. doi: 10.1111/ene.16435. Epub 2024 Aug 8.
Acetylcholine receptor antibody (AChR-Ab) detection is crucial in myasthenia gravis (MG) diagnosis and, currently, the radioimmunoassay (RIA) is the gold standard. However, RIA may detect AChR-Ab against nonpathogenic intracellular epitopes. In this study, we performed fixed cell-based assay (F-CBA) in RIA-AChR-Ab positive subjects without MG symptoms, to assess whether F-CBA could show a higher specificity compared to RIA in detecting pathogenic Abs.
We reviewed medical records of patients referred to our MG outpatient clinic because of RIA-AChR-Ab detection. MG diagnosis was based on clinical examination, electrophysiology and Ab detection. AChR-Abs were tested by RIA in the whole cohort. Serum samples from RIA-positive asymptomatic subjects were retested by F-CBA.
Of 605 subjects who tested RIA-AChR-Ab positive, MG diagnosis was confirmed in 599. Six subjects were RIA-AChR-Ab positive although they had never had MG symptoms; in four of these subjects AChR-Abs were not detected by F-CBA, whereas the remaining two (both non-MG thymoma cases) were positive also by F-CBA.
RIA false positivity for AChR-Ab is very rare. Previous literature has demonstrated that F-CBA has higher sensitivity than RIA for MG, especially in ocular cases. Our preliminary results show that, in rare instances, F-CBA may be more specific than RIA for MG diagnosis.
乙酰胆碱受体抗体（AChR-Ab）的检测对重症肌无力（MG）的诊断至关重要，目前放射免疫分析（RIA）是金标准。然而，RIA 可能会检测到针对非致病性细胞内表位的 AChR-Ab。在这项研究中，我们对无 MG 症状但 RIA-AChR-Ab 阳性的受试者进行了基于固定细胞的检测（F-CBA），以评估 F-CBA 在检测致病性 Abs 方面是否比 RIA 具有更高的特异性。
我们回顾了因 RIA-AChR-Ab 检测而转诊至我们 MG 门诊的患者的病历。MG 诊断基于临床检查、电生理学和 Ab 检测。在整个队列中通过 RIA 检测 AChR-Abs。对 RIA 阳性无症状受试者的血清样本进行 F-CBA 复测。
在 605 例 RIA-AChR-Ab 阳性的受试者中，599 例确诊为 MG。有 6 例受试者尽管从未有过 MG 症状，但 RIA-AChR-Ab 阳性；在这 4 例受试者中，F-CBA 未检测到 AChR-Abs，而其余 2 例（均为非 MG 胸腺瘤病例）也通过 F-CBA 呈阳性。
RIA 对 AChR-Ab 的假阳性非常罕见。既往文献表明，F-CBA 对 MG 的敏感性高于 RIA，尤其是在眼肌型病例中。我们的初步结果表明，在极少数情况下，F-CBA 可能比 RIA 更具特异性，有助于 MG 的诊断。
