Amyloid PET imaging can alter diagnosis and care in the real world

Access to amyloid PET changes the diagnosis and care of many patients in whom the diagnosis of Alzheimer’s Disease is uncertain. Updated results from the large IDEAS study showing the clinical utility of amyloid PET also support a clear link between air pollution and brain amyloid deposits.

Seventy-two percent of people who turned out to be amyloid negative on PET scan had been given a pre-PET diagnosis of Alzheimer’s Dementia and would have been managed accordingly. This striking finding was reported at an update on a major US study given at ADPD 2021 Virtual by Gil Rabinovici (University of California, San Francisco).

The study demonstrates that amyloid PET scans have real-world clinical utility and can improve patient care, as well as having transformed dementia research, said Professor Rabinovici.

Amyloid PET changed at least one aspect of management in 60% of diagnostically uncertain cases


IDEAS can change the world

In the Imaging Dementia -- Evidence for Amyloid Scanning (IDEAS) Study, more than 18,000 people diagnosed within the past two years as having objective mild cognitive impairment (MCI) or dementia had an amyloid PET scan with one of three FDA-approved amyloid-β tracers.

Those enrolled across almost six hundred dementia practices had a diagnosis that was uncertain following comprehensive evaluation by a dementia specialist which included CT/MRI.

Of those with an MCI diagnosis, 55% turned out to be Aβ positive on PET, while this was true of 70% of those with a dementia diagnosis. In 25% of cases overall, an AD diagnosis pre-PET was changed to a non-AD diagnosis following the scan. And in 11% of cases a non-AD diagnosis was changed to AD.


Management change follows change in diagnosis

Overall, having amyloid PET changed management in more than 60% of cases. This composite outcome included change in AD medications (cholinesterase inhibitor or memantine), change in relevant non-AD medications (such as those used to treat cognition or other neurologic disorders), and change in counseling about safety and planning for the future, such as independent living.

PET led to a change in diagnosis in a third of cases

The study, which was directed by the Alzheimer’s Association, compared the care plan decided on when it was assumed there would be no access to amyloid PET with the care implemented 90 days after the results of the scan were made available.



Air pollution linked to PET amyloid pathology

The IDEAS data have shown another real-world effect: living in areas polluted by high concentrations of fine particulate matter (PM2.5) is associated with a significantly higher likelihood of being positive on an amyloid PET scan.1

This association is dose dependent and statistically significant after adjusting for demographic, lifestyle, and socioeconomic factors. IDEAS researchers also looked at ground-level concentrations of ozone, but found no influence on amyloid PET scan positivity.

More IDEAS to follow

Following the success of IDEAS, a recently-launched study will focus on amyloid PET imaging in populations under-represented in the initial trial. Provision of a biorepository for DNA and plasma is part of the new initiative.

It is hoped that by the end of 2021 data and images from the original IDEAS study will be made available to the research community through the Global Alzheimer’s Association Interactive Network (GAINN).


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Our correspondent’s highlights from the symposium are meant as a fair representation of the scientific content presented. The views and opinions expressed on this page do not necessarily reflect those of Lundbeck.


1. Iaccarino L et al. JAMA Neurol 2021;78:197-207