A total of 10 studies assessed the “A” (i.e., Aβ40, Aβ42 and Aβ42/Aβ40 ratio), 7 focused on the “T” (i.e., p-tau181), 17 studies focused on the “N” (i.e., NfL, t-tau) and 5 assessed the “X” (i.e., GFAP) within the ATNX diagnostic framework of AD. Here, GFAP is linked to Alzheimer disease.