However, the peripheral source of GFAP also affects blood GFAP levels, which may affect the accuracy of blood GFAP concentrations for the early diagnosis of AD [9,10,11], considering that the concentration of GFAP in the blood is also related to the degree of amyloid-β (Aβ) degradation and the phosphorylation of tau. This evidence concerns the gene MAPT and Alzheimer disease.