More research is required, and such a test is likely to be years away, but the researchers said the results are promising.
“This research represents an exciting step toward developing a blood test that could help identify Alzheimer’s disease by targeting specific subtypes of tau, one of the key proteins that becomes abnormal as part of the disease changes. Alzheimer’s in the brain, “said Clive Ballard, professor of age-related diseases at the University of Exeter School of Medicine in the UK, who was not involved in the study.
“A Reliable Blood Test for Alzheimer’s Disease Would Be a Great Boost for Dementia Research, Allowing Scientists to Test Treatments at a Much Earlier Stage, Which in turn Could Lead to a Breakthrough for People living with dementia, “said Dr. Rosa Sancho, director of research at Alzheimer’s Research UK, who was also not involved in the study.
Looking for a mutant protein
In a three-part study, researchers from the United States and Sweden measured an abnormal version of the tau protein called p-tau217 and found more of that modified tau in the blood of people with Alzheimer’s disease than in healthy participants.
How does tau get into the blood? It appears to cross the blood-brain barrier.
“The tau protein is modified and clusters abnormally in the brains of people with Alzheimer’s disease and some frontotemporal dementias, and some of this tau protein escapes from the brain into the blood,” said Tara Spiers-Jones, deputy director. from the Center for Discovery Brain Sciences at the University of Edinburgh, which was not involved in the study.
The researchers report that blood tests can distinguish Alzheimer’s disease from other types of dementia and Parkinson’s with a high degree of precision: 89% to 98%.
Additionally, measuring p-tau217 levels can also detect brain changes 20 years before dementia symptoms appear.
“This test, once verified and confirmed, opens up the possibility of an early diagnosis of Alzheimer’s disease before the dementia stage, which is very important for clinical trials evaluating new therapies that could stop or slow down the process of the disease, “noted the researchers, led by Dr. Oskar Hansson of Lund University in Sweden, he wrote.
“These two documents add to the growing evidence that modified tau proteins in the blood can accurately reflect Alzheimer’s disease in the processes that occur in the brain,” said Amanda Heslegrave, principal investigator at the Institute for Dementia Research at UK at University College London, who was not involved in the study.
At your doctor’s office
The formation of brain proteins, amyloid and tau, in groups of amyloid plaques and tau tangles are defining physical characteristics of Alzheimer’s disease, but are difficult to detect without expensive PET scans or invasive spinal taps, neither of which is covered in routinely by insurance.
Doctors are left with verbal and written tests of memory and cognitive decline, combined with interviews with relatives of patients and caregivers about their behavior. That approach makes it difficult to accurately diagnose Alzheimer’s, unlike other types of cognitive decline.
Also, brain scans and spinal tap can only identify beta amyloid plaques, not the tau protein. A tau test is important, experts say: beta amyloid alone is not enough to diagnose Alzheimer’s because some people with high levels do not develop the neurological disease.
The new blood test can detect both amyloid plaques and tau tangles and is highly specific for Alzheimer’s, the experts said.
A third abstract presented at the Alzheimer’s conference found that the test could differentiate between less common frontotemporal dementia, which affects younger people and leads to changes in behavior and personality rather than memory loss, and disease. Alzheimer’s, which illustrates the diagnostic capabilities of the test. These include changes in personality, behavior, and language difficulties.
“These studies (and others) show that blood-based tau is a marker of amyloid pathology. Very interesting and not what would have been predicted 5 years ago,” said John Hardy, president of Molecular Biology of Neurological Diseases at the University College London.
These advances mean that there may come a day in the next few years when your healthcare provider will be able to do a blood test to screen for Alzheimer’s disease while you are in the doctor’s office, according to experts.
“It is very exciting, because we all know that blood tests are really important and necessary as a first step in the clinic, in your general practitioner’s office,” said Maria Carrillo, medical director of the Alzheimer’s Association.
And unlike current screening methods, blood tests could be more easily expanded to screen many people at much less cost.
Early detection and treatment before significant damage to Alzheimer’s disease occurs in the brain could change the rules of the game for people, experts said. The test could also help identify the right people for clinical drug trials.
“We know that brain changes in Alzheimer’s disease can occur decades before symptoms begin to show and the early stages of the disease are likely to be the time when future medications are most effective,” Sancho said.
Carrillo and other experts warn that while it is promising, blood tests still need to be done among asymptomatic people and larger populations.
“We now need longer and larger studies to validate these results and find out if this test could accelerate our ability to develop new treatments for Alzheimer’s disease in the future.” said Fiona Carragher, director of policy and research for the Alzheimer’s Society in the UK.
Ballard agrees: “Although this research seems extremely promising, additional validation is still needed in people from more routine clinical settings, and much work will be needed to achieve standardization of the test in all laboratories.
“Therefore, it could be at least five years before we see an accurate blood biomarker test to detect dementia in the clinic.”
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