By Rhonda L. Rundle
Early diagnosis of Alzheimer´s disease using positron emission
tomography, an imaging technology known as PET, cuts unnecessary drug
therapy and nursing-home care, according to a new study.
"People who have a scan as part of their workup will be less likely to
be misdiagnosed, and that has substantial consequences for what happens
to them in terms of treatment," said Dan Silverman, principal
investigator and an assistant professor of molecular and medical
pharmacology at the University of California at Los Angeles.
The UCLA study comes as the federal Centers for Medicare and Medicaid
Services is considering whether to pay for PET when the tests are
performed to diagnose Alzheimer's disease, and as Alzheimer´s
researchers and advocates debate the merits of the application.
Full-body PET scans cost between $2,000 and $3,000, while those on the
brain, used to diagnose Alzheimer´s disease, cost about $1,000.
Patients who are diagnosed with Alzheimer´s and treated with drug
therapy to slow the progression of the disease can delay by nine months
or more the need for costly nursing-home care, other studies have shown.
For every 100 patients suffering from early cognitive decline,
conventional methods would have falsely attributed the patients´
symptoms to early Alzheimer's in 23 cases, and overlooked eight cases of
the disease, other studies cited by the UCLA team have indicated.
Dr. Silverman´s team used a benefit-risk analysis to show that use of
PET in clinical evaluation would have prevented 11 of the 23 false
positives and five of the eight false negatives. That, in turn, would
reduce by nearly half the number of patients treated with unnecessary
drug therapies, and cut by 62% the number of avoidable months of
nursing-home care. The study, published in the current issue of the
Journal of Molecular Imaging and Biology, builds on earlier studies by
Dr. Silverman and his UCLA colleagues.
Medicare already covers PET for various applications, including
diagnosis and monitoring of many kinds of cancer. Earlier this year, a
Medicare agency panel recommended against approving PET for use in
diagnosing Alzheimer´s disease, and a final decision by the agency is
pending.
The option is being hotly debated. Dr. Silverman is one of many
physicians who have appeared at hearings in Washington to present
evidence in favor of coverage. However, the largest patient advocacy
group, the Alzheimer's Association, is opposing coverage at this time.
"It's a debate going on within the scientific community, and our best
advisers say the evidence isn't there yet" to justify PET scans for
routine diagnosis of Alzheimer´s disease, said Judy Riggs, the group's
acting vice president for public policy. "At best, there are a small
subset of cases where PET scans might add some further element of
certainty, but that additional precision wouldn´t have any impact on
patient outcomes at this time."
Ms. Riggs said the Alzheimer´s group is "hugely excited" about the value
of imaging technology in research, and is constantly reviewing evidence
about clinical use as it pours in.
Dr. Silverman said his latest study was designed, in part, to address
questions being raised by the skeptics and to show how clinical use of
PET can improve care for patients.
Oct 4th, 2002 Wall Street Journal