In summary, the present study argues against an urgent need to substitute the currently widely used C-3-M1-AQP4-DNA-based CBA with LS first described by us in 2010 with an M23-AQP4-DNA-based CBA and, importantly, largely affirms the validity of the numerous studies that used that assay for assessing the frequency of NMO-IgG/AQP4-IgG seropositivity in NMO spectrum disorders (for example, [12,22,26,27,45-50]). This evidence concerns the gene AQP4 and neuromyelitis optica.