Comparison of the sensitivity of anti‐acetylcholine receptor enzyme‐linked immunosorbent assay and radioimmunoassay in different treatment periods

Abstract Objectives Recently, the EUROIMMUN anti‐acetylcholine receptor antibody (AChR Ab) enzyme‐linked immunosorbent assay (ELISA) became commercially available in Japan, but its clinical performance has not been comprehensively researched. This is the first diagnostic evaluation of the AChR Ab ELISA carried out in the Japanese population, including stratification of myasthenia gravis (MG) patients according to the length of treatment. Methods Concentrations of AChR Ab in sera from clinically confirmed MG patients ( n = 85) and non‐MG control participants ( n = 52) were measured and compared between ELISA and radioimmunoassay (RIA). Sensitivity and concordance of the assays were further analyzed in a stratified manner according to the treatment period. AChR Ab concentration was monitored over the treatment periods (0–5 months, n = 7). Results The concordance rate between ELISA and RIA was 87% (ĸ = 0.74). Specificity of ELISA and RIA were 96% and 100%, respectively. Sensitivity was lower in ELISA (62%) compared with RIA (76%). Subgroup analysis showed that the sensitivity of both assays was identical (90%) in the treatment‐naïve and short‐term medicated patients (≤3 years), but decreased in patients undergoing mid‐ and late‐stage treatment. The concentration of AChR Ab showed reducing trends over the treatment period in both ELISA and RIA ( r = 0.915). Conclusions In addition to other considerable benefits of ELISA, such as automation and avoidance of radioisotope waste, its high overall concordance and equal sensitivity with RIA, especially in treatment‐naïve and early‐stage treatment patients, suggest that the ELISA can be a valuable option supporting MG diagnostics in Japan.