Dye developed here may predict Alzheimer's
Share with others:
A compound developed in Pittsburgh could be the key to diagnosing Alzheimer's disease 10 years before it strikes.
A study released Monday by doctors in Finland found that Pittsburgh Compound B, a radioactive dye that attaches to proteins in the brain, was 90 percent effective in correctly predicting the presence of beta amyloid plaques, which are indicators of Alzheimer's.
Published in Archives of Neurology, the study was the first of its kind on living subjects. Previous studies with Pittsburgh Compound B -- PiB for short -- had compared brain imaging results recorded when patients were alive to samples taken after they had died.
The Finnish doctors used brain surgery patients as subjects. They injected the dye intravenously in each and took a scan, then conducted a biopsy of a small chunk of the brain.
Dr. Chester Mathis and Dr. William Klunk, both of the University of Pittsburgh, developed PiB four years ago to help diagnose Alzheimer's, the most common form of dementia. The only way to know for sure now is post-mortem examination of patients.
PiB, if approved, could not only diagnose the disease in living patients but predict its onset. Dr. Mathis said tests have shown that amyloids can appear at least 10 years before Alzheimer's symptoms.
With that kind of advance knowledge, patients can make financial arrangements and talk to their families about where they'll live.
"You can decide ahead of time, when you're not in the fog of the disease and you can't make the decisions for yourself," Dr. Mathis said.
Still, there is no cure for Alzheimer's, which affects an estimated 5.2 million Americans.
According to the Alzheimer's Association, a Chicago-based advocacy organization, the U.S. Food and Drug Administration has so far approved five drugs that slow the worsening of symptoms for six to 12 months, on average, for about half the people that take them.
But experimental treatments that can reverse the disease's course are in the developmental stages, and work continues on them as it does on PiB.
Researchers hope that a way to diagnose the disease, and drugs to combat it, will be available in five to 10 years.
The Finnish study was another step on that road. Of its 10 participants, five had amyloids and five did not, according to the biopsies of small pieces of the right side of their frontal cortexes. The PiB scans matched up for all of them except one.
"Nine out of 10 ain't bad," Dr. Mathis said. "But the one that's a mystery remains a mystery."
He said PiB has been studied on about 4,000 people at 40 to 50 sites around the world, but more studies could be done. For the brain image scans, one needs a positron emission tomography, or PET, facility, and there are 2,000 of those in the United States alone, Dr. Mathis said.
But there are limitations to PiB's use. There is no proof that everyone who tests positive for amyloids will develop the disease. Also, some recent research has downplayed the importance of amyloids as they relate to Alzheimer's.
"The amyloid is almost certainly a player," said Dr. Ronald Petersen, chairman of the medical and scientific advisory council of the Alzheimer's Association.
"Whether it's the cause or the end-all, be-all is another question."
As a result, researchers are trying to attack Alzheimer's in a variety of ways.
"People are not putting all their eggs in that basket," Dr. Petersen said of Alzheimer's research. "It may in the end take a cocktail like we do with HIV."
There remains, however, the question of whether people would even want to know they have a potential precursor for Alzheimer's -- especially when there is no cure. Research subjects are not told the results of these tests, and the doctors acknowledge that until effective treatments hit the market, PiB won't have much value to the average Alzheimer's patient.
"The big question is, 'What can you do about it?' As of today, there's nothing," Dr. Mathis said.
"The great usefulness will be when there is a therapy that can prevent the onset of this disease."
First Published August 13, 2008 12:00 am
