MAPT and Alzheimer disease: An operational framework, called ATN from the biological markers of (A)myloid-β, (T)au and (N)eurodegeneration, has facilitated a transition from a clinical perspective to a biological viewpoint of Alzheimer’s disease, decoupling diagnosis from discrete clinical stages.2,23 Classification into ATN stages requires the designation of individuals as Aβ, tau and neurodegeneration positive or negative.