However, highly standardized and reproducible assays for the detection of anti-AQP4 antibodies are crucial for large multi-centre studies aiming to better define the epidemiological, clinical, and pathological features of patients with NMO and their response to treatment with respect to the patients anti-AQP4 antibody serostatus, as previously pointed out by Fazio and colleagues [37]. Here, AQP4 is linked to neuromyelitis optica.