The Society of Nuclear Medicine and Molecular Imaging and the Alzheimer's Association have issued guidelines for brain amyloid imaging in Alzheimer's disease, suggesting appropriate candidates for this kind of scan should come from three small subsets of patients.
The accumulation of amyloid plaques between nerve cells in the brain is a sign of Alzheimer's, and a negative scan reduces the likelihood that cognitive impairment is due to the disease. A positive scan indicating the presence of moderate to frequent plaques doesn't necessarily mean a patient has Alzheimer's, since such plaques also are present in patients with other neurological conditions.
According to the Amyloid Imaging Taskforce, a joint project of the Alzheimer's Association and SNMMI, 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 candidates include:
- 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.
The task force also concluded that amyloid PET imaging is inappropriate in other cases, as well, such as using it to determine the severity of dementia, or for non-medical reasons, such as those related to issues regarding employment and insurance.
"As amyloid imaging becomes more prevalent in clinical settings, medical professionals must understand how to appropriately utilize the test," SNMMI President Frederic Fahey, SNMMI said in an announcement. "Neurology and dementia experts should order the test only when appropriately indicated, and nuclear medicine and molecular imaging professionals must ensure they have been adequately trained to interpret the results of the scan. Working together, we hope that the information garnered from amyloid PET imaging will aid in diagnosis and play a pivotal role in the development of new treatments for Alzheimer's."