Background: Despite the availability of cell-based assays for aquaporin-4 (AQP4) and myelin oligodendrocyte glycoprotein (MOG) antibodies provincially, outside confirmatory testing is often performed (typically Mayo Clinic Laboratories, USA) when results deviate from expected. It is unknown how often this costly undertaking (upwards of $1,200 CAN) alters diagnosis and management. Methods: We undertook a quality improvement project evaluating the concordance/discordance rate with select chart review in all patients who had cell-based AQP4 or MOG IgG antibody testing at Mitogen Diagnostics (MitogenDx; Calgary, Alberta) and subsequent testing at Mayo Clinic Laboratories from as early as 2010 to July 2020. Results: Preliminary review of data from January 2016 to July 2020 retrieved 145 paired tests; 10 of which were discordant (concordance rate: 93.1%). Chart review confirmed 9 truly discordant cases, often associated with AQP4 or MOG weak-positive results (7/9 cases) or presumed false negative AQP4 results in prototypical neuromyelitis optica spectrum disorder (2/9 cases). Conclusions: Discordant results were rare when comparing MitogenDx local AQP4/MOG antibody test results to those referred out to Mayo Clinic Laboratories, impacting diagnosis and treatment in only 3 patients out of the total. Our results suggest costly outside confirmatory testing of AQP4/MOG antibodies could be reduced.