MAPT and Alzheimer disease: Currently, the use of biomarkers that can identify AD during its asymptomatic phase [138,139,140] is limited to Aβ1–42/Tau levels in cerebrospinal fluid (CSF) and imaging techniques such as the positron emission tomography (PET) that allow the observation of Aβ accumulation in the brain or 18F-fluorodeoxyglucose-PET (FDG-PET) to detect the decrease in glucose metabolic rate.