MAPT and Alzheimer disease: The PET scans should be performed when there is significant uncertainty regarding the etiology of cognitive impairment after a comprehensive assessment by a dementia specialist (see Section 3: Key Definitions), when AD is a diagnostic consideration, and when knowledge of amyloid or tau status is expected to help establish an etiological diagnosis and guide patient management (e.g., to confirm the presence of amyloid plaques in a patient who is a candidate for amyloid-lowering therapy).