Blood Test May Have Power to Predict Alzheimer's
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SUNDAY, March 9, 2014 (HealthDay News) -- A blood test has been developed that can predict with 90 percent certainty whether a senior will suffer from dementia such as Alzheimer's disease within the next few years, researchers report.
The test relies on levels of 10 lipids, or fats, in the bloodstream to estimate the chances of either mild cognitive impairment -- which involves memory loss and a decline in thinking ability -- or the beginnings of Alzheimer's disease.
Low levels of these 10 blood fats can predict impending dementia symptoms with remarkable accuracy, said study author Dr. Howard Federoff, executive dean of the Georgetown University School of Medicine.
"We do not know why all 10 of those lipids are lower in individuals who are predisposed to go on to cognitive impairment," Federoff said. "We can't directly link this to our current understanding of the pathobiology of Alzheimer's disease."
Maria Carrillo, vice president of medical and scientific relations at the Alzheimer's Association, said such a blood test could prove easier to administer than current tests used to detect early onset of the disease.
Doctors now must rely on expensive MRIs and PET scans that are limited in their diagnostic ability.
"Blood-based biomarkers would be a great and useful option -- more accessible, less invasive, easier to gather and less expensive to process," Carrillo said. "Several are under development for preclinical Alzheimer's disease. More research investment in this area is urgently needed."
The new study involved 525 healthy people aged 70 or older who underwent a full blood exam and a battery of neurocognitive tests.
The research team then followed the participants for five years. During the course of the study, 74 of the people slipped into dementia or mild Alzheimer's disease.
Doctors compared their blood to the blood of people who remained mentally sharp, looking for differences. They found that people who later developed dementia started out with low levels of a series of 10 lipids, compared to the other study participants.
They then performed a second study in which they tested the predictive power of the 10-lipid review on a separate group of 40 people. "We showed the blood test would be able to identify people who would develop mild cognitive impairment," Federoff said.
The accuracy of the blood test neither improved nor diminished when researchers added a genetic test looking for a mutant version of the "APOE" gene that has been linked to Alzheimer's.
In fact, they found the blood test predicted dementia with better accuracy than the APOE test alone.
Accurate tests that can determine who will eventually develop Alzheimer's could play a key role in finding a cure for the disease, Federoff said.
With no effective treatments yet available for Alzheimer's disease, the usefulness of an early warning test for older people remains uncertain. However, Federoff believes that existing drugs may still have promise in treating people at risk for Alzheimer's who have not yet developed the illness.
"Will those disease-modifying therapies show promise if you use them in patients at risk for the disease, before the horse is out of the barn, when they are clinically unaffected?" Federoff asked. "Can you delay or perhaps even completely stop the progression to manifestation? I think this opens up a whole new horizon for this type of clinical research."
Carrillo, of the Alzheimer's Association, noted, and Federoff agreed, that further research into the lipids is needed.
"The results, while intriguing, are preliminary," Carrillo said. "They require replication and validation by other scientists in larger and more diverse populations to give them credibility, before further development for clinical use is warranted."
The study results were published March 9 in the journal Nature Medicine.
The study only showed an association between lower levels of the 10 body fats and an increased risk for dementia. It did not prove a cause-and-effect link.
SOURCE: Howard Federoff, M.D., executive dean, Georgetown University School of Medicine, Washington, D.C.; Maria Carrillo, Ph.D., vice president of medical and scientific relations, Alzheimer's Association; March 9, 2014, Nature Medicine