Diagnostic performance and safety of the edrophonium test in myasthenia gravis: a retrospective case-control study

BACKGROUND: Myasthenia gravis (MG) is an autoimmune disorder of the neuromuscular junction. The diagnosis typically relies on clinical features, serologic testing, and neurophysiological assessment but provocation tests such as the edrophonium test can provide rapid supportive information; however, data on its diagnostic performance are limited. Thus, we aimed to evaluate the diagnostic performance and safety of the edrophonium test in MG. METHODS: We conducted a retrospective case–control study of patients who underwent an edrophonium test at the Department of Neurology of the Medical University of Vienna between January 1991 and January 2024. We calculated sensitivity, specificity, and likelihood ratios and performed a multivariable logistic regression analysis to identify variables associated with a positive edrophonium test. Additionally, we assessed the safety of the edrophonium test. RESULTS: We included 182 patients with MG (41.2% female; mean age 55.8 years) and 324 controls (55.2% female; mean age 53.6 years). The edrophonium test had a sensitivity of 83.5% and a specificity of 87.7% in diagnosing MG. Patients with a decrement after repetitive nerve stimulation had higher odds of a positive response to the edrophonium test (OR 3.79, 95% CI 1.48–10.33, p = 0.0067), while odds were lower in patients with MuSK-MG compared to patients with AChR-MG (OR 0.08, 95% CI 0.01–0.82, p = 0.0254). Adverse events were reported in 58 patients (11.5%), in most of whom (53 patients, 91.4%) they were mild. CONCLUSIONS: We provide data on the diagnostic performance and safety of the edrophonium test, supporting its use as an adjunctive diagnostic test for the diagnosis of MG.