Plasma glial fibrillary acidic protein in the visual and language variants of Alzheimer's disease

INTRODUCTIONGlial fibrillary acidic protein (GFAP) in plasma is a proxy for astrocytic activity and is elevated in amyloid-beta (A beta)-positive individuals, making GFAP a potential blood-based biomarker for Alzheimer's disease (AD).METHODSWe assessed plasma GFAP in 72 A beta-positive participants diagnosed with the visual or language variant of AD who underwent A beta- and tau-PET. Fifty-nine participants had follow-up imaging. Linear regression was applied on GFAP and imaging quantities.RESULTSGFAP did not correlate with A beta- or tau-PET cross-sectionally. There was a limited positive correlation between GFAP and rates of tau accumulation, particularly in the language variant of AD, although associations were weaker after removing one outlier patient with the highest GFAP level.DISCUSSIONAmong A beta-positive AD participants with atypical presentations, plasma GFAP did not correlate with levels of AD pathology on PET, suggesting that the associations between GFAP and AD pathology might plateau during the advanced phase of the disease.