Serum Glial Fibrillary Acidic Protein and Retinal Neuronal Loss as Additive Prognostic Markers of Disability in Multiple Sclerosis

BACKGROUND AND OBJECTIVES: In people with multiple sclerosis (pwMS), optical coherence tomography (OCT) quantifies loss of neurons (macular ganglion cell-inner plexiform layer [mGCIPL]) and axons (peripapillary retinal nerve fiber layer [pRNFL]) in the retina. Serum glial fibrillary acidic protein (sGFAP) is a promising astrocytic biomarker to capture disease progression in pwMS. We aimed to investigate the relationship between OCT markers and sGFAP in pwMS and explore their additive value in predicting disability progression. METHODS: PwMS and healthy controls underwent OCT at baseline (BL), excluding eyes with inter-eye asymmetry. Age, sex, and body mass index-adjusted Z scores of sGFAP were calculated. Cross-sectional and longitudinal associations between sGFAP and retinal layers were estimated using linear regression- and mixed-effects models (LMM). The additive effect of BL-OCT and BL-sGFAP on the trajectory of the Expanded Disability Status Scale (EDSS) was estimated using LMM, whereby pwMS were stratified into: group (1): low sGFAP Z score (<3rd quartile, <Q3) and thick mGCIPL (>Q1); group (2): high sGFAP Z score (≥Q3) and thick mGCIPL or low sGFAP Z Score and thin mGCIPL (≤Q1); and group (3): high sGFAP and thin mGCIPL. RESULTS: < 0.001). DISCUSSION: Our findings show a close relationship between astrocytic activation/injury and neurodegeneration in the CNS, measured at the retinal level. Moreover, they highlight an additive role of mGCIPL and sGFAP for identification of pwMS at higher risk of disability worsening.