July 13, 2010 -- Experts from the National Institute on Aging and the Alzheimer's Association have issued suggestions to update the criteria for the diagnosis of Alzheimer's disease.
The new proposed criteria will be the first update in 26 years.
''The last set of criteria for Alzheimer's disease [diagnosis] were originally developed in 1984," says William Thies, PhD, chief medical and scientific officer at the Alzheimer's Association. "We know a lot more now than we did before, so the new criteria are a reaction to that knowledge," he tells WebMD.
The draft reports for the new criteria were presented Tuesday at the Alzheimer's Association International Conference in Honolulu.
The criteria, aimed at better and earlier detection of Alzheimer's disease, cover three stages believed to exist today: pre-clinical Alzheimer's, mild cognitive impairment, and the last stage, Alzheimer's dementia.
An estimated 5.3 million Americans have Alzheimer's disease, most of them 65 and older, according to the Alzheimer's Association.
Behind the Updated Criteria for Diagnosis of Alzheimer's
''We have always heard you have to wait until you die to confirm Alzheimer's disease," says John Morris, MD, a neurologist and director of the Alzheimer's Disease Research Center at Washington University, St. Louis, who was a member of the Alzheimer's disease dementia workgroup for the new criteria.
"Now we have indicators of that brain pathology we can detect in living persons," he tells WebMD. These measures of the brain's pathology in Alzheimer's disease, called biomarkers, often involve imaging. "The most exciting imaging biomarker is the amyloid imaging," he says. (Beta-amyloid is a microscopic protein fragment in the brain believed to be linked with the disease.)
"We also have spinal fluid biomarkers," Morris tells WebMD. "Biomarkers are a really important scientific advance. It gives us confidence that the brain pathology of Alzheimer's is there,'' helping to make an accurate diagnosis, he says.
New Criteria for Diagnosis of Alzheimer's: A Closer Look
The new criteria update previous criteria that were established by a workgroup with experts from the National Institute of Neurological Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association.
The impetus to update those criteria began at an Alzheimer's Association meeting about eight months ago, Thies tells WebMD.
Experts in Alzheimer's disease were tapped to work on the updated criteria.
Among the advances important to consider in setting up the proposed diagnostic criteria, according to the Alzheimer's Association, is:
Changes in the brain triggered by Alzheimer's develop slowly over many years, reflecting the importance of catching the disease earlier.
Genes can help predict a form of the disease known as early-onset Alzheimer's; these genetic observations indicate that the initial brain event that leads to symptoms and the brain changes begin with disordered beta-amyloid metabolism.
An alternative form of the ApoE gene is now known as a major genetic risk factor for the more common late-onset disease.
Much is known about biomarkers and ongoing research is validating these biomarkers.
For each of the stages, the workgroups have suggestions, Morris says.
The first workgroup, on pre-clinical disease , suggests thinking about Alzheimer's disease not just as dementia, but a brain disorder that begins years before symptoms occur. "This pre-clinical stage may be important for future research," Morris says, hopefully leading to intervention strategies and eventually prevention.
The second, on mild cognitive impairment, also suggests incorporating biomarkers to better differentiate the stages of the disease.
The third, on Alzheimer’s dementia, suggests that the inclusion of biomarkers will increase the confidence of the diagnosis.