Test may detect Alzheimer's early

Published: Tuesday, February 1, 2005 at 6:01 a.m.
Last Modified: Tuesday, February 1, 2005 at 12:50 a.m.
WASHINGTON - A highly sensitive new test could lead to a different way to diagnose people with Alzheimer's disease, possibly helping find the illness in its early stages when there might be time for treatment.
While as many as 4 million Americans are thought to suffer from the memory-destroying illness, the only way to diagnose it definitively is by studying brain tissue during an autopsy.
It is important to have some way to diagnose the disease while the patient is still alive, especially during its early stages, so experimental treatments can be evaluated, and to catch it at a time when the disease might be treatable.
The new test, called a bio-barcode assay, is 100,000 times to 1 million times more sensitive than other available tests, Chad A. Mirkin of Northwestern University said in a telephone interview.
It was first used last year in testing for a marker for prostate cancer, and Mirkin said he invited other investigators to suggest subjects for further testing
William L. Klein, also at Northwestern, had done research associating Alzheimer's with a protein in the brain called amyloid-beta-derived diffusable ligand, or ADDL, Mirkin said. So the researchers set out to try and detect ADDL in spinal fluid. They got samples of the spinal fluid of 30 people, 15 with Alzheimer's disease and 15 without.
The researchers found at least some ADDL in all the patients, which Mirkin said is an indication that everyone may have a baseline level of the protein. "What was really encouraging," he said, is that the concentration of ADDL increases as the disease gets worse, so the progression of the illness could be followed.
"Do we have a new diagnostic for Alzheimer's?" Mirkin said. "That's a bit premature."

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