SOuce: http://www.healthcentral.com/news/NewsFullText.cfm?id=510597
(see DaTSCAN Post)

About 1 million to 1.5 million Americans are diagnosed as having
Parkinson's. But in post-mortems -- the only definitive way to diagnose
the disease in the United States -- only 75 percent of them are found to
have it, Tuite says.

"One-quarter have been misdiagnosed" and actually have essential
tremors, Alzheimer's disease or something else, he says.


New Test For Parkinson's Shows Promise 

But it's not yet available in the United States. 

By Nancy Deutsch
HealthScoutNews Reporter 
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TUESDAY, Dec. 3 (HealthScoutNews) -- U.S. physicians will have to
continue to rely on their physical assessment skills to make a diagnosis
of Parkinson's disease. 

In Europe, a new test is making the diagnosis more definitive in at
least 80 percent of cases, advocates say, but the DaTSCAN is unlikely to
reach this side of the Atlantic anytime soon.

The United States lacks a manufacturer of the radioactive isotope
needed, and the isotope must be used within 13 hours of being processed,
making importing it impossible, says Dr. David Tuite, a radiology
resident at Adelaide and Meath Hospital in Dublin, Ireland.

"As they have no manufacturing facility in North America, this prohibits
its use in the U.S.A.," Tuite says.

Tuite presented the findings of an ongoing study of the DaTSCAN today at
the Radiological Society of North America's annual meeting in Chicago.

"We're the first to use it in our country," Tuite says. "I imagine in
time it will become the standard." 

The DaTSCAN is "a radio pharmaceutical which labels dopamine in the
brain," Tuite says. Patients with Parkinson's begin to have symptoms of
the disease after losing 80 percent of the dopamine in their basal
ganglia, a brain region involved in motor control and movement, he
explains.

"The technique requires nuclear medicine facilities" and can be used to
differentiate Parkinson's disease from essential tremors, another
disorder that resembles the tremors of Parkinson's but whose cause is
unknown.

Many people with essential tremors are placed on medication that doesn't
help them and don't receive the medication they should when they are
mistakenly thought to have Parkinson's, Tuite says. 

About 1 million to 1.5 million Americans are diagnosed as having
Parkinson's. But in post-mortems -- the only definitive way to diagnose
the disease in the United States -- only 75 percent of them are found to
have it, Tuite says.

"One-quarter have been misdiagnosed" and actually have essential
tremors, Alzheimer's disease or something else, he says.

For his study, Tuite and his fellow researchers used DaTSCAN on 50
patients thought to have Parkinson's, but whose physicians weren't sure
this was the correct diagnosis. The test proved valuable in confirming
that many patients had the disease and some did not, based on dopamine
levels that were detected. The test was 80 percent accurate at
identifying Parkinson's when a person had it. And it was 30 percent
accurate at giving a negative result if a person did not have
Parkinson's, Tuite says.

The test was most useful in distinguishing whether patients with tremors
had Parkinson's or essential tremors.

Tuite says he has received many requests from patients for the test.

Dr. Abraham Lieberman, medical director of the National Parkinson
Foundation, says that while the DaTSCAN test may prove valuable, he
doesn't consider it "earth-shattering."

It's not entirely conclusive, he says, although it can be used to verify
a diagnosis of Parkinson's in people who have tremors. As Lieberman
notes, this leaves out many people with Parkinson's because "about 30
percent of those with Parkinson's don't have tremors." 

Dr. Kenneth Marek is president of the Institute for Neurodegenerative
Disorders. He says the DaTSCAN test is "part of a larger approach to
improving diagnosis" of Parkinson's disease and potentially halting its
progression.

Marek says the production of high-grade iodine for radioactive isotopes
is limited in North America. Although he uses it for research, he gets
his limited supply from Vancouver, Canada. "This isn't a readily
available source of radioactive iodine."

He says he's heard that companies that manufacture the isotope in Europe
aren't anxious to open a plant in North America due to a lack of
financial incentives. If the isotope and DaTSCAN were available in the
United States, Marek believes it would be a valuable tool "to settle the
diagnostic question."

What To Do

To learn more about Parkinson's disease, visit the Parkinson's Disease
Foundation Inc. or the National Parkinson Foundation.



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