AQP4 and autoimmune encephalitis: This study aimed to identify distinguishing indicators of aquaporin-4 (AQP4) IgG-negative NMOSD and assess their diagnostic value.<h4>Methods</h4>We analyzed four groups: 85 patients with AQP4-IgG-negative NMOSD, 192 with AQP4-IgG-positive NMOSD, 547 with other nervous system autoimmune disorders (e.g., multiple sclerosis, Guillain-Barré syndrome, and viral and autoimmune encephalitis), and 269 healthy controls matched for sex, age, and BMI.A diagnostic model was established using clinical, biochemical, and cerebrospinal fluid (CSF) variables.