Detection of Alzheimer's before symptoms occur

By Dr. Ananya Mandal, MDAug 4 2010

Research is on to detect the dreaded Alzheimer's disease even before any symptoms occur. In a newly proposed diagnostic criteria developed by experts from the National Institute on Aging and the Alzheimer's Association three stages of the disease viz. pre-clinical Alzheimer's, mild cognitive impairment and Alzheimer's dementia are described.

"We want to be ready because labs are churning out all these new possible products and clinical trials are under way, and if the results should be positive, the idea is that they will  work better in someone whose brain is relatively intact so the earlier we can diagnose someone as being on track for Alzheimer's disease, the better these agents may work," says Creighton Phelps, PhD, director of the Alzheimer's Disease Centers Program in the division of neuroscience at the National Institute on Aging in Bethesda, Md.

According to Steven DeKosky, MD, vice president and dean of the University of Virginia School of Medicine in Charlottesville, "If we had a drug that stops or delays the onset of Alzheimer's disease, the demand for this diagnostic criteria would be immediate…When the drugs are ready, we will be ready to identify Alzheimer's disease in all three stages." He added that like in heart disease where risk factors such as high cholesterol and high blood pressure are identified and treated early on the basis of these risk factors so that they do not go on to have a heart attack or stroke, "we want to identify people who are at-risk and have no symptoms and when appropriate, treat them so they never have these symptoms emerge or we can significantly delay their onset."

Earlier Alzheimer's disease was only accurately diagnosed on autopsy but now there are new imaging biomarkers being developed that can help doctors identify risk of Alzheimer's disease earlier. According to Guy McKhann, MD, professor at the Mind/Brain Institute at Johns Hopkins University in Baltimore the brain changes slowly because of the disease and it can be thus detected. He said, "The disease itself starts many years before the dementia appears…these tests are not ready for prime time except under very controlled circumstances."

Marilyn Albert, PhD, a professor of neurology at Johns Hopkins University in Baltimore added, "We don't think they are ready to be used by clinicians in the community yet…These biomarkers and their cut-offs need to be standardized across the board before they can be used outside of research settings." Reisa A. Sperling, MD, an associate professor of neurology at Brigham and Women's Hospital in Boston agrees with Dr. Albert. Scientists are still working on standardizing the tests - making sure that, like a test for cholesterol or prostate cancer, an Alzheimer's biomarker test done in one lab will give the same results as one done elsewhere. The spinal fluid tests can show levels of amyloid and another Alzheimer's protein, tau. But it is not yet known, what levels of amyloid or tau in spinal fluid are abnormal. And measurements of amyloid and tau can vary as much as 30 percent from one research lab to another, said Dr. Albert. "That's why we are very concerned about these measurements being used in clinical settings at the current time."

Dr. McKhann says, "If you have family history of Alzheimer's disease or other concerns about your risk, keep an eye on trials and be open to volunteering."
Meanwhile the group says that the main goal of the proposed guidelines, which are expected to be adopted, is to find signs of the disease much earlier. The State Government has contributed more than two million dollars towards a study into the early detection of Alzheimer's disease. The Minister for Science and Innovation, Bill Marmion, says the funding will enable the foundation to test more than a thousand patients at risk of developing Alzheimer's. "They inject a special tracer agent and the brain can be imaged, and they can do a scan of the brain and look at how this scan compares to a healthy brain and that gives them an early identifier as to whether the onset of Alzheimer's is happening," he said.