Alzheimer’s

Alzheimer’s blood tests predict age at which people with Alzheimer’s disease may experience symptoms, study finds

Tests that could reveal when Alzheimer’s disease will appear, while promising, are not ready for use in otherwise healthy people, scientists say.

By Lewis asked. edited by Claire Cameron

Blood tests to detect a protein involved in Alzheimer’s disease could help predict the age at which the disease might strike people long before they develop symptoms, a new study suggests. But questions remain about precision and uncertainty of these testsand experts warn that the tests are not ready for prime time.

“Although the results are encouraging, they are not yet at the level of significant clinical benefit for individual patients,” says Corey Bolton, a clinical neuropsychologist and assistant professor of medicine at Vanderbilt University Medical Center, who was not involved in the new study. “Alzheimer’s disease is a complex disease with many risk and resilience factors that vary from person to person. These factors can have a large influence on the age of symptom onset and the rate of clinical decline.”

The study included more than 600 people aged 62 to 78 who did not suffer from cognitive impairment. They underwent blood tests to detect a protein called p-tau217, which builds up in the brains of people with Alzheimer’s disease. The researchers then used a test-based model to predict age of disease onset in people without cognitive impairment with three to four years of uncertainty.

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“A key innovation was to estimate when they will develop symptoms,” says Suzanne Schindler, associate professor of neurology at Washington University School of Medicine in St. Louis, co-author of the study. The research was published Thursday in Natural medicine. Several study authors consulted or received funding from companies that perform these blood tests for Alzheimer’s disease. Schindler says she provides unpaid advice to diagnostic companies.

More than seven million Americans live with Alzheimer’s disease and there is no cure. The neurodegenerative disease is associated with the buildup of amyloid plaques and tau tangles in the brain, which can develop for a decade or more before the appearance of visible symptoms such as memory loss or confusion.

Blood tests are increasingly used to detect biological signs of disease. They are much cheaper and easier to administer than traditional diagnostics such as lumbar punctures or positron emission tomography (PET) scans. In the United States, two tests are approved for use in people with symptoms of Alzheimer’s disease:Lumipulse (made by Fujirebio) And Elecsys (manufactured by Roche Diagnostics).

But these tests don’t always accurately predict who will or will not develop Alzheimer’s disease, experts say. And the medical consensus is that they should not be taken by people without symptoms of cognitive decline.

However, detecting Alzheimer’s disease before symptoms appear can be crucial to treating it: although there is no cure for the disease, two drugs have been approved This can slow the rate of progression in some people when the disease is detected early. And clinical trials of these drugs are underway to determine whether treatment could prevent the disease in people with biological signs of the disease but no symptoms. Results are expected in the coming years.

In the new study, Schindler and colleagues tested how well a blood test for p-tau217 could predict the age at which people with the protein would develop symptoms of the disease. They found that these blood or plasma “clocks” could predict how likely and when people would develop symptoms of the disease. Interestingly, the older a person was, the earlier the symptoms appeared.

“So, for example, if you have a positive blood test at age 60, it may take 20 years before you develop symptoms, whereas if you don’t have a positive blood test until age 80, it may only take 10 years,” says Schindler.

Of course, the tests are not infallible. It’s important to note that researchers “don’t recommend this for asymptomatic people,” says Zaldy Tan, a memory and aging specialist at Cedars-Sinai Medical Center in Los Angeles. And a margin of error of three to four years on either side of the diagnosis is “a big window,” he notes, especially if you use that knowledge to make decisions about retirement plans or finances.

“Other medical conditions, such as chronic kidney disease and obesity, appear to have a large impact on circulating levels of these proteins and can greatly influence results, leading to false positives or false negatives,” says Bolton. This study used a type of test that limits the effect of these conditions, he says, but “there are still many unanswered questions about how these blood tests work in various populations.”

Despite their limitations, these tests nevertheless remain useful for diagnosis and treatment planning, says Bolton. People at greater risk of developing the disease could still benefit from interventions such as exercise, a healthy diet and cognitive or social stimulation.

Nathaniel Chin, a geriatrician and medical director of the Wisconsin Alzheimer’s Disease Research Center in Madison, who was not involved in the study, is “impressed and excited” by its results. He hopes researchers will replicate the results in other populations.

The study was funded by a public-private partnership through the National Institutes of Health Biomarkers Consortium Foundation. Schindler notes that the study data is publicly available and anyone can download and analyze it.