First Guidelines Released for Brain Amyloid Imaging in Alzheimer’s Disease Patients

Only recently has it become possible to create high-quality images of the brain plaques characteristic of Alzheimer’s disease (AD) in living individuals by way of positron emission tomography (PET) imaging. Even so, there are still questions of what can be determined from these PET images and which people should have this imaging modality.

To provide guidance for physicians, individuals and families affected by Alzheimer’s, and the public, the Society of Nuclear Medicine and Molecular Imaging (SNMMI; Reston, VA, USA) and the Alzheimer’s Association (Chicago, IL, USA) have jointly published the first criteria for the appropriate use of this imaging technology to aid in the diagnosis of people with suspected AD. The criteria were published online January 28, 2013, 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.

Whereas increased beta amyloid plaques are one of the definitive pathologic characteristics of AD, many elderly people with normal cognition also have elevated levels of these plaques, as do people with disorders other than AD dementia. Therefore, the potential clinical use of amyloid PET requires careful consideration so that its appropriate role may be identified.

To develop the new criteria, the Alzheimer’s Association and SNMMI assembled an Amyloid Imaging Taskforce (AIT) consisting of dementia and imaging specialists to review the scientific literature and develop consensus recommendations for the clinical use of this exciting new technology.

The AIT concluded that amyloid imaging could possibly 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.

According to the AIT, appropriate candidates for amyloid PET imaging include: (1) those individuals who complain of persistent or progressive unexplained memory problems or confusion and who demonstrate impairments using standard tests of cognition and memory. (2) Individuals meeting tests for possible Alzheimer’s, but who are unusual in their clinical presentation. (3) Individuals with progressive dementia and atypically early age of onset (before age 65).

Inappropriate candidates for amyloid PET imaging include: (1) those who are age 65 or older and meet standard definitions and tests for Alzheimer’s, because a positive PET scan would provide little added value. (2) Asymptomatic people or those with a cognitive complaint but no clinical confirmation of impairment.

Amyloid PET imaging is also inappropriate: (1) As a means of determining the severity of dementia. (2) When requested only based on a family history of dementia or presence of other risk factors for AD, such as the ApoE-e4 gene. (3) As a substitute for genetic testing for mutations that cause ADs. (4) For nonmedical reasons, such as insurance, legal or employment decisions.

The taskforce recognized that the healthcare provider has the final say 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: (1) Assessment by dementia specialists to evaluate the need for diagnostic testing, perhaps to include amyloid PET if the AUC are met. (2) Referral to a qualified provider of amyloid PET services. (3) Performance, interpretation and reporting of the amyloid PET scan according to established standards. (4) Integration of the PET finding into the clinical assessment process. (5) Lastly, disclosure of PET findings by the clinician to the patient and caregivers, along with discussion of the result and its management consequences.

Although identifying potential benefits, the AIT concluded that amyloid PET findings will not constitute and is not equivalent to a clinical diagnosis of AD dementia. They reported that imaging is only one approach among many that clinicians should use judiciously to manage patients, and that amyloid PET imaging does not substitute for a careful history and examination.

If an amyloid imaging PET scan shows that a person with memory impairment has amyloid buildup in their brain, this increases the likelihood that the memory impairment is caused by AD, but it remains a probability, not inevitable. If an individual without memory problems or impairment has amyloid accumulation, it does not necessarily mean that they will develop AD.

Related Links:
Society of Nuclear Medicine and Molecular Imaging
Alzheimer’s Association