Results of the Imaging Dementia–Evidence for Amyloid Scanning study were published April 2 in JAMA. IDEAS tested if amyloid PET affected the management or outcomes of dementia care. As reported previously on Alzforum, physicians changed their treatment for 61.5 percent of people based on scan data, well above the prespecified estimate of 30 percent (Nov 2018 conference news). Whether those changes improve how those patients fare has yet to be determined. That second phase of the study ended in February 2019 and will likely be published within a year, said Gil Rabinovici, University of California, San Francisco, IDEA’s lead author.

  • IDEAS asked if PET scans affected clinical management of dementia.
  • Physicians changed treatment for 61 percent of those scanned.
  • Whether those changes affect outcomes remains to be seen.

IDEAS was born of the Centers for Medicare & Medicaid Services’ (CMS) desire to know if reimbursing for these expensive scans would be worthwhile. Sixteen thousand and eight , volunteers with mild cognitive impairment or mild dementia took part. They had no clear diagnosis when enrolled but Alzheimer’s disease had to have been a possibility. They were seen by 946 dementia specialists at 595 U.S. sites. Of the 11,409 who completed the study, 6,971 had a positive PET scan. Diagnosis for 2,860 patients changed from AD to non-AD, and for 1,201 patients from non-AD to AD. Between pre- and 90 days post scan, physicians changed treatment for 7,018 patients. They changed AD drug therapy, other drug therapy, or initiated counseling about safety and life planning. “This supports (but without randomization does not prove) a relationship between the PET findings and post-PET changes in management,” wrote Clifford Jack and Ronald Petersen, Mayo Clinic, Rochester, Minnesota, in a JAMA editorial.

The findings thus far are unlikely to sway the CMS. As Jack and Petersen note, “For CMS to cover the cost of amyloid PET, it must be demonstrated that the result of a scan has an effect on patient outcomes, not just patient care processes—and, without a disease-modifying therapy available, that might be a challenge.”

Whether the second phase of the study might be more persuasive remains to be seen. Rabinovici and colleagues have followed these patients for a year to see if those who received a PET scan had fewer visits to the hospital or emergency room. “The premise is that if you have a clear diagnosis at an early stage, then you can incorporate safety steps and better drug management to prevent bad outcomes down the road,” said Rabinovici.

Rabinovici and the CMS are discussing a new IDEAS study to address gaps in the first. It would be more diverse, recruiting 2,000 African Americans and 2,000 Latinos to increase their representation above the 4 percent level in the current IDEAS study.

It would also recruit people with probable AD and genotype them for ApoE, since one-third of those with a clinical diagnosis of probable AD and no ApoE4 allele in past studies have tested negative for amyloid. “ApoE4 genotyping might help stratify the risk of having amyloid to help us avoid having to scan everyone,” Rabinovici said.

Additionally, participants in this medical practice-based study would have the option to donate DNA and plasma. This could help refine polygenic risk scores and validate markers identified in cohort studies, such as ADNI.—Tom Fagan


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News Citations

  1. Amyloid PET Aids Diagnosis. But Could CSF Do Just as Well?

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