MAPT and Alzheimer disease: These PET biomarkers have led to the proposal of the term “preclinical AD” when the risk is particularly high (e.g., both Aß and tau markers exceed the pathological thresholds) and “asymptomatic at risk for clinical AD” (AR-AD) when the evolution to clinical AD is less likely or has yet to be confirmed (only one pathophysiological PET marker considered abnormal) (65).