This classification categorizes individuals based on AD biomarkers, dichotomized as follows (i.e., positive or negative): “A” for β-amyloid abnormalities (at the amyloid PET scan or CSF Aβ 42 measurement), “T” for tau protein changes (via tau PET scan, or CSF phospho-tau assessment), and “N” for evidence of neurodegeneration (through [18F]-fluorodeoxyglucose–PET, structural MRI, or CSF total tau determination). This evidence concerns the gene MAPT and Alzheimer disease.