Nov 30, 2020 - Health

First blood test to help diagnose Alzheimer's goes public

Photo of two masked scientists looking at a row of beakers

Photo: Jerry Naunheim Jr./C2N Diagnostics via AP

A non-COVID medical breakthrough: People over 60 now have access to a blood test for Alzheimer's disease.

Why it matters: The existing PET brain scan test costs some people about $5,000 and often isn't covered by insurance, AP reports.

  • Both the blood test and the brain scan are looking for a buildup of a protein called beta-amyloid, which combined with symptoms like memory loss can lead to a dementia diagnosis.
  • The test hasn't received FDA approval, and it's being sold under rules for commercial labs.

The big picture: Roughly 5.5 million Americans may have Alzheimer's-induced dementia, the NIH reports.

  • Earlier diagnoses can't stop the disease, the NIH notes, but treatments can prolong the period before people lose the ability to function on their own.

Between the lines: C2N Diagnostics of St. Louis, which is selling the test and seeking FDA approval, hasn't published any data on the test's accuracy, AP notes.

  • Company promotional materials cite results comparing the test to PET brain scans.
  • If a PET scan showed amyloid buildup, the blood test also gave a high probability of that in 92% of cases and missed 8% of them.
  • If the PET scan was negative, the blood test ruled out amyloid buildup 77% of the time. The other 23% got a positive result. Published research suggests it may detect amyloid buildup before it’s evident on scans.

The other side: Heather Snyder of the Alzheimer’s Association told the AP the organization won’t endorse a test without FDA approval.

The bottom line: “It’s not a cure, it’s not a treatment, but you can’t treat the disease without being able to diagnose it," Alzheimer's researcher Dr. Michael Weiner told the N.Y. Times when the research was first published.

  • "And accurate, low-cost diagnosis is really exciting, so it’s a breakthrough."
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