Concordance of repetitive nerve stimulation test at low frequencies and AChR in myasthenia gravis

Objective: The objective of the study was to determine diagnostic concordance between repetitive nerve stimulation test at low frequencies (LF-RNST) and anti-nicotinic acetylcholine receptor (AChR) in myasthenia gravis (MG).Methods: We performed a retrospective longitudinal observational concordance study.After authorizing the protocol of the Physical Medicine and Rehabilitation service patient registry, the clinical records that met the selection criteria were selected, and the following variables were recorded: positive LF-RNST, negative LF-RNST, negative AChR, positive AChR, diagnosis of confirmed MG, and diagnosis of ruled out MG. Results: A total of 106 records were included in this study, with an unweighted Cohen's kappa coefficient agreement of 0.952, a 95% confidence interval for patients with both positive tests and a confirmed diagnosis of MG, and an unweighted Cohen's kappa coefficient of 0.544, a 95% confidence interval for patients with both negative tests and a diagnosis of discarded MG.Conclusions: The LF-RNST could be very similar to the AChR test if performed in patients with MG.