GFAP and early-onset autosomal dominant Alzheimer disease: However, no difference was found between A+T− and A+T+ groups, in line with previous results and suggesting that an increase in GFAP represents an early event in Alzheimer's disease pathogenesis.12 Although results in the previous section agree with the strong correlation between plasma GFAP and amyloid pathology, it was also found that amyloid PET distribution was not significantly correlated with GFAP at a voxel level when corrected for other covariates.