The first criteria for the appropriate use of positron emission tomography (PET) to aid in the diagnosis of Alzheimer disease (AD) have been published jointly by the Society of Nuclear Medicine and Molecular Imaging and the Alzheimer’s Association.
Elevated levels of beta amyloid plaques in the brain are one of the defining pathologic features of AD. However, many otherwise normal elderly people have increased levels of these plaques, as do patients with conditions other than AD. Therefore, the clinical utility of PET imaging for beta amyloid plaques requires careful consideration.
The new guidelines state that appropriate candidates for amyloid PET imaging include patients with persistent or progressive unexplained mild cognitive impairment; patients satisfying core clinical criteria for possible AD (that is, atypical clinical course or etiologically mixed presentation); and patients with atypically young-onset dementia.
Conversely, such imaging is not appropriate for the diagnosis of patients who have core clinical criteria for probable AD with typical age of onset; for patients with a cognitive complaint that is unconfirmed on clinical examination; or for asymptomatic individuals.
Amyloid PET imaging also should not be used: to determine dementia severity; when based solely on a positive family history of dementia or presence of apolipoprotein E e4; in lieu of genotyping for suspected autosomal mutation carriers; or for nonmedical usage, such as for insurance, legal, or employment decisions. Medicare currently does not cover beta amyloid PET imaging.