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First Appropriate-Use Guidelines for Brain Amyloid Imaging in Alzheimer's Disease

PET technology is important diagnostic aid but must be used judiciously (Jan. 28)

Only recently has it become possible to create high-quality images of the brain plaques characteristic of Alzheimer’s disease (AD) in living people through positron emission tomography (PET). Even so, questions remain about what can be learned from these PET images and which people should undergo this test.

To provide guidance for physicians, individuals, and families affected by AD, the Society of Nuclear Medicine and Molecular Imaging (SNMMI) and the Alzheimer’s Association have jointly published the first criteria for the appropriate use of PET imaging technology to aid in the diagnosis of people with suspected AD. The criteria were published online as an article “in press” in Alzheimer’s & Dementia and “ahead of print” in the Journal of Nuclear Medicine.

To develop the new criteria, the SNMMI and the Alzheimer’s Association assembled an Amyloid Imaging Taskforce (AIT) consisting of dementia and imaging experts to review the scientific literature and to develop consensus recommendations for the clinical use of PET in patients with AD.

According to the AIT, appropriate candidates for amyloid PET imaging include:

  • Those who complain of persistent or progressive unexplained memory problems or confusion and who demonstrate impairments using standard tests of cognition and memory.
  • Individuals meeting tests for possible AD but who are unusual in their clinical presentation.
  • Individuals with progressive dementia and an atypically early age of onset (i.e., before the age of 65).

Inappropriate candidates for amyloid PET imaging include:

  • Those who are aged 65 years or older and meet standard definitions and tests for AD, since a positive PET scan would provide little added value.
  • Asymptomatic people or those with a cognitive complaint but no clinical confirmation of impairment.

Amyloid PET imaging is also inappropriate:

  • As a means of determining the severity of dementia.
  • When requested solely based on a family history of dementia or the presence of other risk factors for AD, such as the ApoE-e4 gene.
  • As a substitute for genetic testing for mutations that cause AD.
  • For nonmedical reasons, such as insurance, legal, or employment decisions.

The AIT concluded that amyloid PET results will not constitute, and are not equivalent to, a clinical diagnosis of AD dementia. They said that imaging is only one tool among many that clinicians should use judiciously to manage patients, and that amyloid PET imaging is not a substitute for a careful history and examination.

PET uses radioactive drugs to produce three-dimensional functional images of the brain or another body part. In amyloid PET imaging, the radiopharmaceutical is introduced into the body by injection into a vein and binds specifically to the amyloid protein, thereby enabling visualization of areas in the brain where amyloid has clumped together into plaques. A new PET compound was approved for general use by the FDA in April 2012.

Source: SNMMI; January 28, 2013.

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