The world’s first blood test to identify Alzheimer’s disease was recently developed to predict the onset of the neurodegenerative disease. The test identifies 10 chemicals in the blood associated with Alzheimer’s and it could detect the disease three years before the signs and symptoms could even occur.
Howard Federoff at Georgetown University in Washington DC and his colleagues studied 525 people aged 70 in a five-year study. The group showed no signs of mental impairment at the start of the study, and each year, the team performed detailed cognitive examination and took blood samples from all participants. During this time, 28 people developed the disease or mild cognitive impairment, though to be at the earliest noticeable sign of dementia, including Alzheimer’s disease.
Blood analysis of the participants highlighted 10 metabolites that were depleted in those with mild cognitive impairment who went on to get Alzheimer’s compared with those who didn’t. In following trials, the team showed these chemicals could predict who would go on to get Alzheimer’s within the next three years with up to 96% accuracy.
Globally, the World Health Organization (WHO) reports that 35.6 million are living with Alzheimer’s and the number is feared to be doubled by 2030 and triple by 2050. Alzheimer’s is characterized by toxic buildup of amyloid and tau proteins in the brain, which destroys the neurons. Blood tests can diagnose the disease, but until now, none had the sensitivity to predict its onset.
Much Earlier Warning
The next step in the research is to refine the the blood test. Federoff said in an interview that he would like to determine if the lipid changes can be detected sooner, about 10 to 20 years sooner.
It is hoped the blood test will someday be available in doctors‘ offices, since the only methods for predicting Alzheimer’s right now, such as PET scans and spinal taps, are expensive, impractical, often unreliable and sometimes risky.
Mark Mapstone at University of Rochester Medical Center in New York says that the 10 metabolites play a key role in supporting cell membranes, maintaining neurons or sustaining energy processes.
“These metabolic changes might occur 10 or 20 years earlier – that would give us a real head start on predicting the disease,” he says. The test could be able to predict the disease much earlier, because the brain changes associated with Alzheimer’s begin many years before symptoms occur. Once the test is verified in a larger group, it should provide a cheap and quick way of predicting Alzheimer’s.
The team is hoping to investigate this by looking back at other dementia studies in which blood has been taken over decades and seeing whether the chemical changes can be detected that early, says Federoff.
The researcher team also analyzed the patients’ full genome sequence and the genetic changes that took place over the five-year period are an even stronger predictor of future cognitive impairments.
“The gene changes are linked to the metabolite changes, so we’re hoping to put all this together to provide a more complete description of the underlying pathology of the disease,” Federoff says. “What’s more exciting is that we know the function of all affected genes, so if we can intercept these changes, they might make a good candidate for new drugs.”
Alzheimer’s Crystal Ball
But with still no cure available, would anyone want to take the test?
Mapstone says yes. “In my experience, the majority of people are very interested to know whether they will get Alzheimer’s. They believe that knowledge is power – particularly when it comes to your own health. We may not have any therapy yet but there are things we can do – we can get our financial and legal affairs in order, plan for future care, and inform family members.”
Implications to the quality of life could be huge if the test can predict the disease 20 years before the symptoms appear. “Imagine, what you would do in your early 40s to slow the onset of the disease. You could eat the right foods, avoid head trauma or do more exercise.”
Other studies have shown that early detection is valuable in the treatment of neurodegenerative diseases so a blood test of this nature could have a considerable impact on drug development and quality of lifestyle to those who have it.
The new test will be valuable for drug discovery efforts according to Tracy Young-Pearse, a neurologist at Harvard Medical School. Years of failed drug trials have shown that you have to catch the disease early to have any influence.
Three researches are starting this year in hope just to do that. One will test anti-amyloid drugs on healthy people with a rare mutation that gives them early onset Alzheimer’s by age 45.
The second will take advantaged of a chemical developed last year that will be injected into the body and can accumulate in tau tangles. It will allow researchers to track the progression of tau in the living brain.
The third trial will investigate whether anti-amyloid drugs can prevent the disease in older people who don’t yet have memory problems but do have amyloid building up in their brain.