Tau-PET levels are strongly associated with cognitive changes in the preclinical and prodromal stages of AD,2,3 outperforming amyloid-PET, fluorodeoxyglucose (FDG)-PET, and structural MRI in direct comparisons.3-5 Among tau tracers, 18F-flortaucipir is the most widely used and the only US Food and Drug Administration (FDA)–approved test establishing biomarker evidence of AD in living people. The gene discussed is MAPT; the disease is Alzheimer disease.