The Society of Nuclear Medicine and Molecular Imaging and the Alzheimer’s Association Amyloid Imaging Taskforce (AIT) have jointly published the first criteria for the appropriate use of brain amyloid imaging technology to aid in the diagnosis of people with suspected Alzheimer's disease. The criteria were published online as an article "in press" by Alzheimer's & Dementia®: The Journal of the Alzheimer's Association and "ahead of print" in The Journal of Nuclear Medicine.
The AIT concluded that amyloid imaging could potentially be helpful in the diagnosis of people with cognitive impairment when considered along with other clinical information, and when performed according to standardized protocols by trained staff. In addition, they emphasized that the decision whether or not to order amyloid imaging should be made only after a comprehensive evaluation by a physician experienced in the assessment and diagnosis of cognitive impairment and dementia, and only if the presence or absence of amyloid would increase certainty in the diagnosis and alter the treatment plan.
The AIT is currently reviewing the existing appropriate use criteria for amyloid PET imaging and determining criteria for tau brain imaging.
Appropriate use criteria
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 Alzheimer's, but who are unusual in their clinical presentation.
- Individuals with progressive dementia and atypically early age of onset (before age 65).
Inappropriate use criteria
Inappropriate candidates for amyloid PET imaging include:
Amyloid PET imaging is also inappropriate:
- Those who are age 65 or older and meet standard definitions and tests for Alzheimer's, since a positive PET scan would provide little added value.
- Asymptomatic people or those with a cognitive complaint but no clinical confirmation of impairment.
- As a means of determining the severity of dementia.
- When requested solely based on a family history of dementia or presence of other risk factors for Alzheimer's, such as the ApoE-e4 gene.
- As a substitute for genetic testing for mutations that cause Alzheimer's.
- For non-medical reasons, such as insurance, legal or employment decisions.
Appropriate sequence of events
The taskforce acknowledged that the healthcare provider makes the ultimate judgment regarding the care of each patient. The AIT sought to assist this process and identified the following general sequence of events for the use of amyloid PET according to the new criteria:
- Evaluation by a dementia expert to assess the need for diagnostic testing, possibly to include amyloid PET if the appropriate use criteria are met.
- Referral to a qualified provider of amyloid PET services.
- Performance, interpretation and reporting of the amyloid PET scan according to established standards.
- Incorporation of the PET result into the clinical assessment process.
- Disclosure of the PET result by the clinician to the patient and caregivers, along with discussion of the result and its potential management consequences.
Although identifying potential benefits, the AIT concluded that amyloid PET results will not constitute and is not equivalent to a clinical diagnosis of Alzheimer's disease dementia. They said that imaging is only one tool among many that clinicians should use judiciously to manage patients, and that amyloid PET imaging does not substitute for a careful history and examination.
Future update of appropriate use criteria
In 2020, the Alzheimer's Association, in collaboration with the Society of Nuclear Medicine and Molecular Imaging (SNMMI), convened a workgroup of experts to review the current data to update the 2013 appropriate use criteria (AUC) for amyloid PET. This update is in progress now, and will include AUC for both amyloid and tau brain imaging.