MAPT and Alzheimer disease: Blood-based AD biomarkers reflecting amyloid, tau, and neurodegeneration (ATN) may be keys to early diagnosis and underlie the National Institute on Aging and Alzheimer’s Association 2018 research framework8; the framework mandates research based on ATN, with or without clinical manifestations, to better understand the mechanisms underlying AD, the temporal sequence of AD neuropathologies, and the temporality of factors associated with increased risk of AD.