Alzheimer’s blood test can predict what age people will be when symptoms of the disease appear, study finds
Scientists say tests that could predict when Alzheimer’s disease will emerge are not yet ready for use in healthy people, while promising.
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A blood test that detects proteins involved in Alzheimer’s disease may help predict at what age people may develop the disease, even before they develop symptoms, according to a new study. But questions remain about the accuracy and uncertainty of these tests, and experts warn that the tests are not ready for prime time.
“Although the results here 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 condition with many interconnected risk and resilience factors that vary from person to person. These factors can have a major impact on the age of symptom onset and the rate of clinical decline.”
The study involved more than 600 people aged 62 to 78 who were not cognitively impaired. They conducted a blood test to detect a protein called p-tau217, which accumulates in the brains of people with Alzheimer’s. The researchers then used a model based on the tests Estimate the age of disease onset In people without cognitive impairment, the age of three to four years is uncertain.
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“A major innovation was predicting when they would develop symptoms,” says study co-author Suzanne Schindler, an associate professor of neurology at Washington University School of Medicine in St. Louis. This research was published on Thursday naturopathy. Many of the study authors have consulted for or received funding from companies that conduct Alzheimer’s blood tests. Schindler says she provides unpaid consulting to diagnostic companies.
More than seven million Americans suffer from Alzheimer’s disease, and there is no cure. The neurodegenerative condition is associated with the formation of plaques of amyloid protein and tangles of tau protein in the brain, which can develop for a decade or more before visual symptoms such as memory loss or confusion occur.
Blood tests are increasingly being used to detect biological signs of disease. These are much cheaper and easier to administer than traditional diagnostics such as spinal taps or positron-emission tomography (PET) scans. Two tests have been approved for use in people with Alzheimer’s symptoms in the US—Lumipulse (manufactured by Fujirebio) And Alexis (manufactured by Roche Diagnostics).
But experts say these tests can’t always accurately predict who will get Alzheimer’s and who won’t. And the medical consensus is that they should not be taken by people who do not have symptoms of cognitive decline.
However, detecting Alzheimer’s before symptoms appear can be key to treating it: Although there is no cure for the condition, two drugs have been approved that can slow the rate of progression in some people if the disease is caught early. And clinical trials of these drugs are underway to determine whether treatment can eliminate the disease in people who have biological signs of the disease but no symptoms. Results are expected in the next few years.
In the new study, Schindler and colleagues tested how well a blood test for p-tau217 could predict at what age people who had the protein would develop symptoms of the disease. They found that these blood, or plasma, “clocks” could predict when and how people would develop disease symptoms. Interestingly, the older the person, the sooner the symptoms appear.
“So, for example, if you have a positive blood test at age 60, it may take 20 years for symptoms to develop — conversely, if you don’t have a positive blood test until age 80, it may take only 10 years,” Schindler says.
Of course, the tests are not infallible. It’s important to note that researchers “are not recommending it for people who don’t have any symptoms,” says Zeldy Tan, MD, a memory and aging expert at Cedars-Sinai Medical Center in Los Angeles. And the error margin of three to four years on either side of the diagnosis is “a big window,” he notes, especially if you’re using the knowledge to make decisions about retirement plans or finances.
“Other medical conditions, such as chronic kidney disease and obesity, have a major impact on the circulating levels of these proteins and can significantly influence the results, leading to false positive or false negative results,” says Bolton. This study used a type of test that limits the impact of these conditions, he says, but “there are still many unanswered questions about how these blood tests perform in different populations.”
Despite their limitations, the tests are still valuable for diagnosis and planning treatment, Bolton says. People found to be at higher risk of developing the disease may 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 findings in other populations.
The study was funded by a public-private partnership through the National Institutes of Health Biomarkers Consortium Foundation. Schindler says the study data are publicly available and anyone can download and analyze them.
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