The hypothesis of this work is that the combination of a few neurodegeneration biomarkers in plasma (p-Tau181, NfL, and GFAP) could provide high sensitivity and specificity for the early diagnosis of AD (defined as mild cognitive impairment (MCI-AD)), as well as discriminating between early AD and other neurocognitive diseases (FTD and LBD). This evidence concerns the gene GFAP and Cognitive impairment.