Waters and colleagues studied AQP4 autoantibodies in NMO and LETM patients by tissue-based IIFA, FIPA and a similar cell-based IIFA; and reported that 14 of 24 NMO patients (58%) were seropositive by tissue-based IIFA, 19 of 25 NMO patients (76%) seropositive by FIPA and 20 of the 25 NMO patients (80%) seropositive by cell-based IIFA. This evidence concerns the gene AQP4 and neuromyelitis optica.