Alzheimer's Scan Might Help Spot Disease01/21/11
FRIDAY, Jan. 21 (HealthDay News) -- An advisory panel's
recommendation that the U.S. Food and Drug Administration approve a
new chemical that can highlight the telltale signs of Alzheimer's
in brain scans may one day help doctors diagnose the
neurodegenerative disease, experts said Friday.
On Thursday, the panel voted 16 to 0 to recommend approval of
the imaging agent, known as Amyvid, with one critical caveat:
Manufacturer Eli Lilly and Co. must demonstrate that standards for
interpreting brain scans that show amyloid plaques illuminated by
Amyvid can be made consistent enough to routinely guarantee an
Amyvid (florbetapir) is injected into patients who then undergo
a PET scan; a negative result can help rule out Alzheimer's,
according to Lilly.
Experts agreed that the test could become a critical part of
spotting Alzheimer's before symptoms have taken hold, but they
noted that the clinical reality of that is far from imminent.
"It may well be that amyloid imaging will join colonoscopy, mammography, etc. as mid-life surveillance tests, and that anti-amyloid interventions are most effective in the pre-symptomatic stages of Alzheimer's disease," said Dr. Sam Gandy, the Mount Sinai Chair in Alzheimer's Disease Research in New York City. However, this possibility is years away, he added.
The value for research is clear, Gandy said. "Either a spinal
fluid amyloid test or an amyloid scan will help weed out
non-Alzheimer's dementias in clinical trials of anti-amyloid
agents. The clinical value in the short-term is less obvious."
Current medications are most effective in the early stages of
Alzheimer's, and amyloid scans might identify those patients for
doctors who don't have access to neuropsychological testing, Gandy
"A confirmed diagnosis would enable planning for the future while patients are at an early enough stage to still participate in the discussion," he said. "In the symptomatic patient, the amyloid scan would portend the onset of dementia within the next five years."
However, because there is no cure for Alzheimer's disease yet,
the test might be one that is not considered worth its cost, Gandy
Gandy noted that the "300-pound gorilla in the room" is whether
Medicare/Medicaid will reimburse such a test, even if the FDA
follows its expert panel's advice and approves Amyvid. (While the
FDA doesn't have to follow a panel's advice, it usually does.)
"Medicare may decide that the added value does not merit
reimbursement without a meaningful intervention," he said.
Also, Grandy said he doesn't expect approval until there are
methods in place to train doctors in how to read these scans.
Another expert, David Loewenstein, a professor of psychiatry and
behavioral sciences and neurology at the University of Miami Miller
School of Medicine, said that the approval of Amyvid "will allow
physicians to come to an earlier diagnosis of Alzheimer's."
What is needed is consistency for evaluating scans using the
agent, he said, so that physicians "can apply a single standard and
there won't be gaps between hospitals because of different readers
using different methods."
Loewenstein thinks use of this new diagnostic tool will help in
several ways. First, it will help researchers find effective
treatments by diagnosing the disease early, although having the
plaques does not always mean the patient has Alzheimer's. Second,
it will identify people who can take part in clinical trials of new
"There is a whole new line of drugs being formulated that will help treat the earliest stages of the disease," Loewenstein said. "We need to know who are the appropriate people with the mildest cognitive problems to get into clinical trials."
In addition, the test has value even before treatments are
available in terms of helping patients prepare for the course of
the disease, Loewenstein noted. "I think many people would like an
early diagnosis," he said.
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