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New chemical gives insight into Alzheimer's
2006-12-21
A chemical designed by doctors in Los Angeles could give unprecedented insight into the ravages of Alzheimer's disease and provide a new way to test for treatments, a study showed on Wednesday. Previously the only way to determine if a person suffers from the devastating brain ailment has been to remove some brain tissue or with an autopsy. The new study by doctors at the University of California, Los Angeles, is part of a larger quest to find a better method to diagnose the condition using tracers that can be detected with a positron emission tomography, or PET, scan. The chemical, known as FDDNP, attaches to the abnormal clumps of proteins called amyloid plaques and tau tangles that develop in Alzheimer's sufferers and inhibit messages being processed by the brain. In the study to be published in Thursday's New England Journal of Medicine, Gary Small and his colleagues discovered that the chemical allowed doctors to pick out which of 83 volunteers had Alzheimer's, which had mild memory problems, and which were functioning normally for their age. It was 98 percent accurate in determining the difference between Alzheimer's and mild cognitive impairment. That was far better than the 87 percent success rate for a PET scan test that measured sugar metabolism in the brain, and the 62 percent accuracy rate when doctors used a magnetic resonance imaging scan to gauge brain deterioration. "You can see the (telltale FDDNP) signal in people years before they get Alzheimer's," Small said. His team also found that the distribution of the FDDNP in the brain of Alzheimer's patients matched the pattern seen in people where the diagnosis is confirmed with an autopsy. "If patients get worse clinically, we see a buildup of the FDDNP binding. That suggests we can track the disease over time," Small said. Finding an easier way to track brain deterioration not only would help doctors diagnose the disease, it could become easier to assess experimental Alzheimer's treatments, as researchers try to prevent the accumulation of plaques and tangles, or to reduce them if they accumulate. Small and four of the other 15 authors named in the research paper have a financial interest in FDDNP, which has been licensed to the German conglomerate Siemens AG. He said he hopes to see it on the market within three years. About 4.5 million people in the United States have Alzheimer's and that number will grow as the population ages. Roughly 15 million to 20 million more have the mild cognitive impairment that often leads to Alzheimer's. Other researchers trying to track the progress of the disease are looking for telltale signs in spinal fluid or with a FDDNP-like chemical from the University of Pittsburgh known as PIB. But PIB can only find plaques and it disappears from the body 5.5 times faster than FDDNP. One problem plaguing Alzheimer's tests is that the results are not always clear-cut. For example, some people who seem to have few memory problems can have a positive result on a test.
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