Further specialist investigations if Alzheimer's disease suspected

If the diagnosis is uncertain and Alzheimer's disease is suspected, consider either:

• FDG-PET (fluorodeoxyglucose-positron emission tomography-CT), or perfusion SPECT (single-photon emission CT) if FDG-PET is unavailable or
• examining cerebrospinal fluid for:
  • either total tau or total tau and phosphorylated-tau 181 and
  • either amyloid beta 1-42 or amyloid beta 1-42 and amyloid beta 1-40
• If a diagnosis cannot be made after one of these tests, consider using the other one.

Notes:

• the older a person is, the more likely they are to get a false positive with CSF fluid exam
• do not rule out Alzheimer's disease based solely on the results of CT or MRI scans.
• do not use apolipoprotein E genotyping or electroencephalography to diagnose AD
• be aware that young-onset Alzheimer's disease has a genetic cause in some people.

Reference:

• (1) NICE (June 2018). Dementia: assessment, management and support for people living with dementia and their carers. (Accessed 15 March 2022)