Health & Medicine

This brain scan changes how doctors treat Alzheimer’s. Here’s why it’s so hard to get.

Dementia study looks at Alzheimer’s disease in the brains of diverse populations

UC Davis study looks at if the mixture of dementia and Alzheimer's disease in the brains across the population.
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UC Davis study looks at if the mixture of dementia and Alzheimer's disease in the brains across the population.

Researchers at the Alzheimer’s Association and the University of California reported results of a new study Tuesday, showing that when doctors were able to definitively diagnose Alzheimer’s disease using brain scans, they changed their patients’ treatment in roughly two-thirds of the cases.

Researchers said they had not expected the brain scan results, which used positron emission tomography, to have such a big impact on diagnoses and treatment, but that doctors and patients clearly benefited from seeing whether Alzheimer’s telltale amyloid plaques were visible in images.

Today, people generally rely upon postmortem examination of autopsied brains to conclusively diagnose whether a loved one had Alzheimer’s disease, characterized by both amyloid plaques and tau protein “tangles” in the brain. With amyloid PET scans, radiologists inject patients with “tracer” molecules that stick to amyloid plaques and use them to identify plaque location.

The U.S. Food and Drug Administration has approved three different versions of PET imaging that can detect amyloid plaques, but the technology is generally available to patients in only top medical research centers because most insurers won’t cover the cost. The Centers for Medicare and Medicaid Services have a significant influence on whether treatments are covered, and they say they have not seen enough evidence of clinical benefit.

Consequently, the Alzheimer’s Association brought together researchers to invest time in this four-year study, which involves more than 11,000 Medicare beneficiaries, nearly 1,000 dementia specialists, 700 imaging specialists, and 595 practices around the United States. As part of this research, Medicare agreed to reimburse each institution for the cost of amyloid PET scans.

Managed by the American College of Radiology, the research drew upon the knowledge of scientists at the Alzheimer’s Association, UC San Francisco, Brown University School of Public Health, Virginia Commonwealth University School of Public Health, Washington University School of Medicine in St. Louis, UC Davis School of Medicine and the Kaiser Permanente Division of Research.

“These results present highly credible, large-scale evidence that amyloid PET imaging can be a powerful tool to improve the accuracy of Alzheimer’s diagnosis and lead to better medical management, especially in difficult-to-diagnose cases,” said Maria C. Carrillo, the chief science officer at the Alzheimer’s Association and a study co-author.

Alzheimer’s has no cure, but early diagnoses allow physicians to prescribe symptom-management therapies, counsel families on safety and care-planning issues, and direct patients to clinical trials for promising drugs. In addition, many families face lengthy periods of indecision or uncertainty about what to do to protect a relative legally and financially because there is no definitive diagnosis.

The newly published study reveals that doctors changed their clinical management of more than 60 percent of patients, more than double the number the authors had predicted in advance. The PET scan provides an objective tool for diagnosis of Alzheimer’s rather than relying on a physician’s neurological examinations.

Here’s what the study showed:

  • Providers were two times more likely to prescribe drug therapies following PET imaging – about 40 percent prior to imaging vs. 82 percent following scans – in the participants who showed mild cognitive impairment but whose brain scans showed significant amyloid plaques.

  • Prescriptions rose to about 91 percent from 63 percent in individuals who had dementia and significant amyloid buildup present in PET scans.
  • One in three patients had been given a diagnosis of Alzheimer’s disease, but their PET scans showed there wasn’t a significant buildup in plaques.
  • Almost half of those not previously diagnosed with Alzheimer’s actually had the indicative buildup of plaque in their brains.
  • Researchers also looked at individuals who had been referred to drug trials because they had a diagnosis of Alzheimer’s, and they found that a third of them had no sign of an amyloid buildup in their brains.

Dr. Gil Rabinovici, a neurology professor at UCSF Memory and Aging Center who co-chaired the study with Carrillo, said: “Accurate diagnoses are critical to ensure patients are receiving the most appropriate treatments. In particular, Alzheimer’s medications can worsen cognitive decline in people with other brain diseases. But perhaps more fundamentally, people who come into the clinic with concerns about memory problems want answers. An early, definitive diagnosis may allow individuals to be part of planning for the next phase of their lives and to make decisions that otherwise would eventually need to be made by others.”

Rabinovici, Carrillo and the rest of their research team are continuing with the next phase of their research, examining how amyloid PET scans affect health outcomes. They are reviewing CMS claims to document hospitalization rates and emergency department visits for study participants and then comparing that data to participants with similar neurological problems but who did not undergo the brain scans.

In other words, will a definitive diagnosis of Alzheimer’s and changes in treatment have any impact on clinical outcomes?

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