Rapid Test Can Predict Alzheimer’s Risk Decades Before Symptoms

Researchers at Mass General Brigham have discovered that a blood test measuring the biomarker plasma phosphorylated tau 217 (pTau217) can predict the progression of Alzheimer’s disease in cognitively healthy older adults. The findings, published in Nature Communications, indicate that this biomarker can detect early signals of the disease years before brain scan changes or clinical symptoms emerge.

The study suggests that pTau217 testing may allow for simpler and earlier disease prediction, helping to identify individuals who are at a higher risk for cognitive decline long before the onset of symptoms.

Study Methodology and Participant Data

The findings are based on a prospective cohort study that followed 317 cognitively healthy older adults from the Harvard Aging Brain Study. The participants in the study ranged in age from 50 to 90 years and were monitored for an average of eight years.

Throughout the study period, researchers utilized a combination of diagnostic tools to track the progression of the disease. These included blood tests for pTau217, repeated tau and amyloid PET scans, and long-term cognitive testing.

The investigators specifically examined whether the baseline levels of pTau217, as well as changes in those levels over time, could predict the future abnormal buildup of misfolded tau proteins inside brain neurons, the accumulation of amyloid, and overall cognitive decline.

The research revealed that higher levels of pTau217 were predictive of a faster buildup of Alzheimer’s disease pathology. Notably, this predictive capability remained evident even in cases where the participants’ initial brain scans appeared normal.

Advancing the Timeline of Detection

For years, amyloid PET scans were considered the most effective method for the earliest possible detection of Alzheimer’s progression. These scans can typically reveal amyloid accumulation in the brain 10 to 20 years before symptoms appear.

However, this new research indicates that blood-based biomarkers may push the window of detection even further back. Hyun-Sik Yang, MD, a neurologist with the Mass General Brigham Neuroscience Institute and an associate member of the Broad Institute of MIT and Harvard, who also serves as a Harvard Medical School assistant professor of neurology at Brigham and Women’s Hospital, noted the shift in detection capabilities.

Regarding the previous reliance on imaging, Yang stated, We used to think that PET scan detection was the earliest sign of Alzheimer’s disease progression, revealing amyloid accumulation in the brain 10 to 20 years before symptoms appear, adding that now we are seeing that pTau217 can be detected years earlier, well before clear abnormalities appear on amyloid PET scans.

Clinical and Regulatory Context

The development of these blood tests follows a significant regulatory milestone in 2025, when the U.S. Food and Drug Administration cleared the first blood test for Alzheimer’s disease. This clearance created a pathway for diagnostic options that are less invasive and more affordable than traditional lumbar punctures or PET scans.

The study by Yang and colleagues provides additional evidence for the predictive potential of these blood-based tests, suggesting they could eventually streamline how the medical community identifies at-risk populations.

Future Applications and Limitations

Despite the predictive potential of pTau217, researchers caution that It’s currently too early to recommend this specific blood test for general screening in older adults.

The primary goal for the researchers is to establish the test as a scalable screening tool for clinical trials. By identifying individuals at a higher risk for Alzheimer’s disease earlier, these trials can better target prevention strategies before irreversible damage occurs.