Limited availability of live CBA for AQP4-IgG testing and its consequences for the diagnosis and treatment of NMOSD in Latin American countries.

According to the 2025 IPND consensus, live cell-based assays (live CBA) are now established as the reference standard for screening AQP4-IgG autoantibodies in patients suspected of having AQP4-IgG-positive Neuromyelitis optica spectrum (NMOSD). However, resource-limited settings in Latin America (LATAM), where even commercial kits (fixed CBA) can be scarce, face significant difficulties in accessing local live CBA due to its higher implementation cost, the time required for experimentation, and its technical complexity. In this narrative review, we identified 85 published studies that provide evidence of CBA locally used in LATAM countries. We identified 18 studies (21.1%) that used "live CBA" as the exclusive AQP4-IgG testing method. Brazil was the only country that had participated in all these reports. Argentina (n = 2, 2.3%), Mexico (n = 1, 1.1%), and Colombia (n = 1, 1.1%) have participated in studies combining "live CBA and fixed CBA". Our literature review suggests that live CBA availability is approximately 20% when considered as a single testing method, or up to 27.1% (n = 23) when used to varying degrees in conjunction with fixed CBA. Notably, several studies (n = 37, 43.5%) we analyzed relied solely on commercial fixed assays for AQP4-IgG testing. Worryingly, nearly one-third (n = 25, 29.4%) of the studies we analyzed still use commercial kits in combination with other non‑gold-standard methods to detect AQP4-IgG. In general, fixed CBA was the most sensitive method in 62 studies (72.9%) from LATAM. Based on our findings, here, we critically discuss the pressing need for live CBA dissemination across LATAM countries. This initiative will lead to more accurate epidemiological data, enable faster diagnosis, and improve access to highly effective therapies for AQP4-IgG-positive NMOSD patients living in this part of the world.