Detecting Alzheimer's Early: A New Test

Up to now, the only definitive way to diagnose Alzheimer's disease has been to study brain tissue during an autopsy, much too late to do anything about it. A new test developed by two researchers at Northwestern University could help physicians diagnose and treat Alzheimer's much earlier in the game. The bio-barcode assay test, said to be up to 1 million times more sensitive than others, detects a protein in the brain -- amyloid-beta-derived diffusable ligand (ADDL) -- associated with Alzheimer's. (The same test was used last year to detect a marker for prostate cancer.)

Researchers compared samples of spinal fluid from 30 patients, evenly divided between those who did and didn't have Alzheimer's. Researchers detected some level of ADDL in each patient, implying a baseline of the protein exists. Also, the concentration of ADDL increases as the disease gets worse, so the progression of Alzheimer's could be followed.

Nevertheless, scientists weren't ready to proclaim victory just yet, citing the need for the process to be repeated on more patients and more studies on ADDL levels in relation to other diseases related to memory loss.

Why is this test called "bio-barcode"? To detect ADDL, researchers used nanoscale particles that had antibodies specific to these small soluble proteins. Some particles were magnetic and others of gold with strings of DNA attached. These antibodies bind to ADDL, sandwiching the protein between the two particles. Then, ADDL is removed from the solution magnetically and the hundreds to thousands of DNA strands attached to the gold particles serve as a barcode because they can be used to label the specific target with standard detection methods.

Not surprising people are so interested in tests like this one, considering the recent spike in Alzheimer's cases foreshadows a potential "public health disaster" that could potentially turn into an unmanageable health care crisis. What's important for you to understand: Alzheimer's disease is not a normal part of aging, and there are natural and safer ways to reduce your chances of succumbing to it.

USA Today February 1, 2005

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