MAPT and Alzheimer disease: We note that the A+T− group is complex and could be a confounding factor for investigations into diagnostic power, as it may indicate an early stage of Alzheimer's progression (amyloid positivity but not yet tau) or the positivity to amyloid might be a comorbidity (secondary) to another neuropathology not measurable with AD biomarkers (e.g., TDP‐43).