Cerebrospinal 14-3-3 Protein Levels as a Neuroaxonal Biomarker in Aquaporin-4 Antibody-Positive Neuromyelitis Optica Spectrum Disorder

Background and Objectives To investigate whether CSF 14-3-3 protein levels discriminate aquaporin-4 antibody-positive neuromyelitis optica spectrum disorder (AQP4-NMOSD) from myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) and multiple sclerosis (MS) and the association of CSF 14-3-3 protein levels with clinical features in patients with AQP4-NMOSD. Methods This was a multicentric retrospective cohort study of patients with AQP4-NMOSD, MOGAD, and MS, with available CSF samples. 14-3-3 protein levels were quantified using ELISA and compared between the 3 conditions. In patients with AQP4-NMOSD, the association between CSF 14-3-3 protein levels and disability outcomes was explored. Results A total of 134 patients were included (AQP4-NMOSD, n = 29; MOGAD, n = 43; MS, n = 62). Patients with AQP4-NMOSD had higher 14-3-3 protein levels (median [interquartile range] 4,441.37 [3,240.05-11526.41] arbitrary units (AU)/mL) compared with those with MS (3,169.86 [2,522.65-3,748.57], p = 0.001) and MOGAD (3,112.95 [2,367.37-3,889.43], p = 0.004). Patients with AQP4-NMOSD presenting with optic neuritis had lower 14-3-3 levels compared with those with other phenotypes (p < 0.001). In AQP4-NMOSD, 14-3-3 levels associated with Expanded Disability Status Scale (EDSS) at attack (beta [95%CI] 0.33 [0.15-0.52], p = 0.003) and predicted final EDSS >= 6.0 (odds ratio 9.48 [1.69; 194.34]; p = 0.041) in patients with myelitis. Discussion The study suggests a potential role of CSF 14-3-3 protein levels as a biomarker of neuroaxonal damage in AQP4-NMOSD, because of its ability to correlate with disease severity and predict poor clinical recovery. Classification of Evidence This study provides Class IV evidence that in individuals presenting with acute myelitis, CSF 14-3-3 differentiates AQP4-NMOSD from MS or MOGAD with a sensitivity of 0.60 (0.30-0.80) and specificity of 0.95 (0.84-1.00).