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- A new study uses existing blood tests to model when someone might develop Alzheimer's symptoms.
- The study looks at p-tau217, a blood biomarker used to detect amyloid plaques, which are key markers of Alzheimer’s disease.
- Experts say these results could be very useful in further research for staging the disease, but warn that a comprehensive workup is still needed to diagnose Alzheimer's.
According to the NIH, Alzheimer's disease accounts for up to two-thirds of dementia cases in people 65 and older. The disease can be diagnosed through a comprehensive workup with a healthcare provider who reviews medical and family history, checks current medications, performs a cognitive assessment, and requests blood tests to rule out underlying conditions or causes of dementia. Given the prevalence of Alzheimer's disease and how debilitating it can be, experts are very interested in diagnostic tools that can help manage symptoms and treatments as early as possible.
Now, the latest study shows that researchers have used existing blood tests to better pinpoint how likely people are to develop Alzheimer's disease, down to the year when symptoms might surface. Still, experts say the estimates they give about future Alzheimer’s disease development aren’t quite ready for use at your local doctor’s office or at home.
Here’s what the data show, plus what this means about diagnosing Alzheimer’s disease going forward.
Meet the experts: Clifford Segil, DO, a neurologist at Providence Saint John’s Health Center in Santa Monica, California; Suzanne Schindler, MD, PhD, study co-author and neurology researcher at Washington University in St. Louis School of Medicine; Davide Cappon, PhD, director of neuropsychology at Tufts Medical Center.
What did the study find?
The study, published in Nature Medicine, analyzed data from over 600 older adult volunteers who participated in two long-running Alzheimer’s disease research initiatives.
The researchers developed models that looked at a protein called p-tau217 in a person’s plasma collected via diagnostic blood tests to estimate the age at which someone would begin experiencing symptoms of Alzheimer’s disease. P-tau217 is a blood biomarker used to detect amyloid plaques, key markers of Alzheimer's disease. (If p-tau217 sounds familiar, it might be because last year, the first FDA-cleared blood test to diagnose Alzheimer's disease used p-tau217 and another protein to detect the disease.)
The latest findings allowed researchers to develop a “clock model” using existing blood tests to estimate when p-tau217 levels first became abnormal, says Suzanne Schindler, MD, PhD, study co-author and neurology researcher at Washington University in St. Louis School of Medicine. “The estimated age at p-tau217 abnormality is correlated with the age at which individuals develop Alzheimer’s symptoms,” she explains.
This means the p-tau217 blood tests can help predict when individuals will develop symptoms, though Schindler points out that "these estimates are still rough," with an error of about 3 to 4 years.
What do experts think?
The findings are “a really interesting step forward,” says Davide Cappon, PhD, director of neuropsychology at Tufts Medical Center. “For years, we’ve become much better at detecting the biology of Alzheimer’s disease—especially with blood biomarkers like p-tau217—but what has been much harder is estimating the timeline of symptoms,” he says.
But Cappon says it’s important to interpret the results with caution. “The prediction window is still a few years, and Alzheimer’s progression varies a lot from person to person,” he says, adding that he sees this test as "less of a clinical tool right now and more as an important step in how we think about staging the disease for research.”
There's also the possibility that reliance on these biomarker tests without other clinical neurological exams and clinician oversight will result in more false positives, points out Clifford Segil, DO, a neurologist at Providence Saint John's Health Center in Santa Monica, California.
Segil warns that using a blood test like this without comparing it to other confirmatory markers, such as brain scans and spinal fluid biomarkers, could lead to misdiagnosis or create a disease timeline that isn't entirely accurate. “Studies like this are supportive that dementia is a simple disease that can be diagnosed with a blood test like diabetes, prostate cancer, or hypothyroidism...which it is not,” he says.
The takeaway
It’s important to point this out: The test isn’t new, per se. “The current study looks at several clinically available p-tau217 blood tests in cognitively unimpaired research participants,” Schindler says. However, Cappon explains, the new model's ability to use the same biomarker to estimate the timing (not just presence or absence) of Alzheimer's symptoms is what's notable. He adds, “As therapies move earlier in the disease course, understanding where someone sits along that trajectory may become increasingly important.”
Schindler and her team are currently working to fine-tune the test, but they're not there yet. “Currently, these estimates are not accurate enough for individual-level use and decision-making—they are only for research purposes and clinical trials,” she says.
So, while the results of this study might not lead to an over-the-counter home test, the research could still be very helpful to clinicians and researchers in developing more treatments for Alzheimer's down the line.
Carina Hsieh, MPH, is the deputy features editor of Women’s Health. She has more than a decade’s worth of experience working in media and has covered everything from beauty, fashion, travel, lifestyle, pets, to health.
She began her career as an intern in the fashion closet at Cosmopolitan where she worked her way up to Senior Sex & Relationships Editor. While covering women’s health there, she discovered her passion for health service journalism and took a break to get her Masters in Public Health. Post-grad school, she worked as a freelance writer and as The Daily Beast’s first Beauty, Health, and Wellness Reporter.
Carina is an alum of the Fashion Institute of Technology and the Yale School of Public Health. She and her French Bulldog, Bao Bao, split their time between Brooklyn and Connecticut. She enjoys reformer Pilates, (slow) running, and smelling the fancy toiletries in boutique fitness class locker rooms.
