Alzheimer’s Study Finds PET Scan Affects Patient Diagnosis, Management

The results are the first part of a national study of whether a method to detect Alzheimer’s-related plaques improves the outcomes of patients with mild cognitive impairment and dementia.

A national study, published in the Journal of the American Medical Association, found that brain imaging to detect Alzheimer’s-related plaques affected clinical diagnosis and management of patients with mild cognitive impairment and dementia. The findings are a step toward understanding how imaging results ultimately affect patient outcomes.

Constantine Gatsonis, Ph.D. (below), Henry Ledyard Goddard University Professor of Statistical Sciences and Director of the Center for Statistical Sciences, was the lead statistician for the first of- its-kind national study which included 11,409 Medicare beneficiaries, 595 different clinical sites, and 946 dementia specialists.

The team found that providing clinicians with the results of positron emission tomography (PET) scans that identify amyloid plaques in the brain changed medical management—including the use of medications and counseling about dementia risks—in more than 60 percent of patients. This information also altered the diagnosis as to the cause of cognitive impairment in more than one in three study participants.

Gatsonis shared insights on the Imaging Dementia: Evidence for Amyloid Scanning (IDEAS) study and his role as lead statistician.

What is the overall goal of the IDEAS study?

Currently, the Centers for Medicare and Medicaid Services (CMS) does not provide financial coverage for amyloid PET scans—they need more clinical evidence. The IDEAS study was funded to provide evidence on the impact of amyloid PET testing. The first aim of the study is to see if the results of an amyloid PET changed how clinicians managed these patients. The second aim is to see if the scan cuts down on subsequent health care utilization. This study is not about the accuracy of Alzheimer’s diagnosis— studies of the accuracy of amyloid PET have already been done. This study was done to see if this imaging scan has an impact on the patient.

What are amyloid plaques and how does this method detect them?

Amyloid plaques are deposits of protein “clumps” in the brain. Previous studies have shown that amyloid plaques are predictive of Alzheimer’s disease.

In general, a PET scan is a nuclear scan. The patient is injected with an agent marked with a radioactive substance that binds to the target of interest. The three agents we used show a pattern when the amyloid plaque is there. Because PET scans are somewhat fuzzy, PET is combined with a CT—so you do the PET at the same time you take an x-ray computed tomography scan of the brain so you know where everything is. Previous studies have shown if this test is positive, you have an 80 to 90 percent chance of eventually getting Alzheimer’s.

What findings are being unveiled in this JAMA paper?

The first aim of the study, which is reported in this paper, answers the question of whether knowing the results of the PET scan affected the treatment decisions made by the patients’ physicians. We saw that the PET scan produced substantial changes in clinician assessment of the disease and that clinicians changed their treatment of these patients. But we haven’t shown yet if we’ve made a real measurable difference in terms of patient outcomes. That’s the next paper.

What was your role in the study?

At the Center for Statistical Sciences (CSS) we do a lot of large, multi-center studies of imaging. For example, screening studies for lung cancer and breast cancer. For the IDEAS study, CSS was deeply involved in formulating the scientific questions of the study. There was a lot of brainstorming done upfront about what is it that we’re going to evaluate, how might we evaluate it, and how will we organize the study to evaluate it? Once the study got going, CSS monitored the data collection, and we are now doing the data analysis.

What are the next steps of the IDEAS study?

The second main question of the study is: Does the scan cut down on health care utilization? The idea here is that if somebody has an early warning from the PET scan, then can they can start planning changes in their living arrangements and behavior or somebody could monitor them more carefully. This may ultimately reduce hospitalizations and visits to the emergency room. A lot of hospitalizations and other health care utilization for dementia patients come about because they stop being able to take care of themselves—people who are diabetic forget to check their blood sugar or to take heart medications, for example.

So we linked the data on people in the IDEAS study with their Medicare claims data. We now know how many times they visited the hospital and other health care utilization patterns for the year after the scan. We also went into the Medicare database and found matched controls for the participants in the study— people in the same area as the original participants with similar characteristics, but who did not receive a PET scan. We’re seeing if the IDEAS participants who had the amyloid PET scan had different amounts of health care utilization compared to similar Medicare beneficiaries who did not have the scan.