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While it’s a life-altering disease, Alzheimer’s disease isn’t always easy to diagnose. Other conditions can have similar symptoms, and some people may not notice cognitive changes until the disease is farther along. And though there are blood tests that suggest someone may have Alzheimer’s disease, they don’t always show the full picture.
Now, new research funded by the National Institutes of Health (NIH) suggests that an experimental blood test may help pick up patients who are on the verge of developing symptoms, allowing healthcare providers to intervene sooner.
The new test isn’t available to the public yet, but it’s very different from what’s currently on the market. Here’s what you need to know about this test, plus what neurologists who treat patients with Alzheimer’s disease think about it.
Meet the experts: Clifford Segil, DO, a neurologist at Providence Saint John’s Health Center in Santa Monica, California; and Krishnankutty Sathian, MBBS, PhD, chair of neurology at Penn State Health Milton S. Hershey Medical Center.
What did the study find?
The study analyzed the effectiveness of a new test that detected elevated levels of specific circular RNAs (circRNAs) in the blood. The current blood tests for Alzheimer’s disease look for markers of amyloid plaques, which are hallmarks of the disease. But these don’t give much information on how a patient’s disease will progress.
To examine the new test, researchers analyzed blood test data from more than 1,200 people and built a model from 34 circRNAs linked to Alzheimer’s disease. They compared this with existing predictive models that focused on the pTau217 protein, the leading clinical blood-based biomarker for Alzheimer’s.
Researchers found that the circRNA test performed similarly to the pTau217 test in identifying biomarker-confirmed Alzheimer’s patients. But the new test was better at predicting which cognitively unimpaired people would later progress to having symptoms of Alzheimer’s disease. The data suggest that levels deviate from normal about 2 to 4 years before someone develops symptoms.
How does this differ from current blood tests?
Current blood tests measure proteins (like pTau217) that are linked to the amyloid plaques associated with Alzheimer’s, explains Clifford Segil, DO, a neurologist at Providence Saint John’s Health Center in Santa Monica, California. “Rather than placing a needle into your spine to look for these protein levels, blood tests looking for these proteins have been marketed as ‘biomarkers’ or blood tests looking for these high proteins,” he says.
But this new test measures a type of genetic material known as circular RNA, which detects biological changes linked to the disease, says Krishnankutty Sathian, MBBS, PhD, chair of neurology at Penn State Health Milton S. Hershey Medical Center.
Why does this matter?
Dr. Sathian calls this an “exciting development” because it has the potential to find Alzheimer’s disease-related changes in the brain earlier than current tests. “It may even help predict which individuals are most likely to develop symptoms over time,” he says. “That's an important distinction, since some people have Alzheimer's pathology, but remain cognitively normal throughout their lives due to factors such as cognitive reserve or resilience.”
This means you can take a blood test that says you have markers that indicate Alzheimer’s disease—without having symptoms. It’s for this reason, Dr. Segil says, that most neurologists won’t diagnose Alzheimer’s disease from a blood test alone. “Diagnosing people with dementia from a blood test will result in people who do not have dementia being told they have dementia or false positives,” he says. “Most people would not want a family member or themselves diagnosed with dementia from a blood test.”
Where might this fit into current Alzheimer's testing?
More research is needed first. But if the new test proves effective in further research, Dr. Sathian says it may be a good screening tool for older adults. “It could eventually be incorporated into routine preventive care, such as Medicare Annual Wellness Visits, or used earlier for individuals at higher risk for Alzheimer's disease,” he says. “However, further validation is needed before it becomes part of standard clinical practice.”
What happens now?
More research is in the works. However, the scientists behind the test are working with companies to develop tests for clinical use.
