Modified and improved anti-acetylcholine receptor (AchR) antibody assay: comparison of analytical and clinical performance with conventional anti-AChR antibody assay.

We developed a modified anti-acetylcholine receptor (AChR) antibody (Ab) assay based on a radioreceptor assay and a calibration curve. We compared the analytical and clinical performances of this modified assay with those of the conventional anti-AChR Ab radioreceptor assay. Serum specimens were from patients with myasthenia gravis (MG) (n = 156) and from control subjects (n = 106). The modified assay demonstrated lower within-assay (4.0-6.6%) and between-assay (5.3-7.8%) CVs, greater linearity, lower cost, and shorter assay time than the conventional method. ROC curve analysis indicated almost identical specificity and sensitivity (> 0.92) for these two anti-AChR Ab assays. The modified and conventional assays were also equivalent for blocking anti-AChR Ab assay. Moreover, the modified anti-AChR Ab assay, differently from the conventional assay, allowed us to reveal anti-AChR Ab concentration differences among different clinical grades of MG.