Serum glial fibrillary acidic protein correlates with retinal structural damage in aquaporin-4 antibody positive neuromyelitis optica spectrum disorder

Abstract

BackgroundAquaporin-4 immunoglobulin-G positive (AQP4-IgG+) neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune astrocytopathy associated with optic neuritis (ON). Myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) is an oligodendrocytopathy with a similar phenotype. Serum glial fibrillary acidic protein (sGFAP), an astrocyte-derived protein, is associated with disease severity in AQP4-IgG+ NMOSD. Serum neurofilament light (sNfL) indicates neuroaxonal damage. The objective was to investigate the association of sGFAP and sNfL with subclinical afferent visual system damage in clinically stable AQP4-IgG+ NMOSD and MOGAD patients. MethodsIn this cross-sectional study, clinically stable patients with AQP4-IgG+ NMOSD (N = 33) and MOGAD (N = 16), as diseased controls, underwent sGFAP and sNfL measurements by single molecule array, retinal optical coherence tomography and visually evoked potentials. ResultsHigher sGFAP concentrations were associated with thinner ganglion cell-inner plexiform layer (β (95% confidence interval (CI)) = −0.75 (−1.23 to −0.27), p = 0.007) and shallower fovea (average pit depth: β (95%CI) = −0.59 (−0.63 to −0.55), p = 0.020) in NMOSD non-ON eyes. Participants with pathological P100 latency had higher sGFAP (median [interquartile range]: 131.32 [81.10–179.34] vs. 89.50 [53.46–121.91] pg/ml, p = 0.024). In MOGAD, sGFAP was not associated with retinal structural or visual functional measures. ConclusionsThe association of sGFAP with structural and functional markers of afferent visual system damage in absence of ON suggests that sGFAP may be a sensitive biomarker for chronic disease severity in clinically stable AQP4-IgG+ NMOSD.