AQP4 and neuromyelitis optica: Relying on the rapid automated plate reader IgG measurements, we identified astrocyte-specific IgG in nine of 36 (25%) IND [patients considered: four AQP4+ NMO and one GFAP+ astrocytopathy for the validation cohort; six seronegative NMOSD, 12 suspected AIE/PNS and 13 OIND as part of the exploratory cohort] versus two of 57 (3.5%) NIND patients (pF= 0.003; Figure 2A).