The Anti-NMO Antibody (Aquaporin 4 Antibody) test checks for specific antibodies in your blood that target aquaporin-4 (AQP4) water channels, key in diagnosing Neuromyelitis Optica Spectrum Disorders (NMOSD), a rare autoimmune disease affecting the optic nerves and spinal cord. This blood test, often called the AQP4-IgG test, helps distinguish NMOSD from Multiple Sclerosis (MS) and predicts future attacks, allowing for earlier, targeted treatment to prevent severe vision loss, weakness, and paralysis, using steroids or other medications