Original IDEAS Study

The strongest Phase IV data to date supporting the clinical utility of amyloid PET scanning

The original IDEAS Study was developed in response to the 2013 Centers for Medicare and Medicaid Services (CMS) National Coverage Decision on amyloid PET imaging in dementia and neurodegenerative disease. CMS did not provide coverage for the scans, stating “the evidence is insufficient to conclude that the use of positron emission tomography (PET) amyloid-beta (Aβ) imaging is reasonable and necessary for the diagnosis or treatment of illness or injury or to improve the functioning of … Medicare beneficiaries with dementia or neurodegenerative disease.”

CMS questioned the ability of PET amyloid imaging to lead to improved health outcomes, such as avoidance of futile treatment or tests, improving quality of life or slowing its decline, and survival. However, CMS did find sufficient evidence that the use of PET Aβ imaging is promising: (1) to exclude Alzheimer’s disease (AD) in narrowly defined and clinically difficult diagnoses, and (2) to enrich clinical trials seeking better treatments or prevention strategies for Alzheimer’s. Under the National Coverage Decision, Medicare would provide coverage for one amyloid PET scan per patient enrolled in an approved clinical study.

The Alzheimer’s Association decided to lead an initiative to bring stakeholders together to develop a Coverage with Evidence Development program. The IDEAS Study team was formed and protocol development began. The study opened in February 2016 and concluded recruitment in January 2018. The study engaged 946 dementia experts, who recruited Medicare beneficiaries from 595 dementia clinics and referred the subjects for imaging at 343 PET facilities across the United States. In total, 18,295 Medicare beneficiaries age 65 and older meeting appropriate use criteria (AUC) were enrolled into one of two sub-groups: (1) progressive, unexplained mild cognitive impairment (MCI), and (2) dementia of uncertain cause. See additional information regarding the methodology and results of Aim 1 of the IDEAS Study. Publication of the results for Aim 2 of the study is anticipated in 2022.


The IDEAS Study team hypothesized that implementing amyloid PET scanning in patients with uncertain diagnoses of cognitive impairment and/or dementia would lead to higher diagnostic certainty, changing patient management and leading to improved outcomes.

The aims of the study were as follows:

AIM 1: Determine if amyloid PET associated with a ≥30% change in composite patient management endpoint between the pre-PET and post-PET visit, separately in MCI and dementia.

  • Total sample size 11,050; 80% power within MCI and dementia subgroups.

  • Patient management changed in 60.2% of MCI and 63.5% of dementia patients.
    • Most common change was in use of AD medications (Increased in Aβ PET+, decreased in Aβ PET-).

  • Diagnosis changed in 35.6% of patients.
    • Increase in diagnostic confidence.
    • Decreased utilization of alternative diagnostics.

AIM 2: Determine if amyloid PET is associated with a ≥10% reduction in 12-months CMS claims-derived hospital admissions and emergency department (ED) visits in study patients vs. controls.

  • Results planned for publication in 2022.
The IDEAS Study has provided the strongest Phase IV data to date supporting the clinical utility of amyloid PET scanning.