The most extensively evaluated AD-related plasma biomarkers include Aβ, especially Aβ40, Aβ42, and their ratio Aβ42/Aβ40, and phosphorylated tau (p-tau) protein at epitopes 181, 217, and 231 (p-tau181, p-tau217, and p-tau231) which reflect neuritic plaques and neurofibrillary tangle pathologies [116,117,118]. This evidence concerns the gene MAPT and Alzheimer disease.