Blood test p-tau217 predicts Alzheimer's risk with high accuracy

A simple blood test can now predict an individual's risk of developing Alzheimer's-related cognitive impairment years before symptoms appear. A major international study found that people with very high levels of the biomarker phosphorylated tau 217 (p-tau217) in their blood had a 38% estimated chance of developing cognitive impairment within five years.

The research was presented at the Alzheimer's Association International Conference and published in JAMA. It analyzed data from 2,684 older adults across North America, Japan, and Australia who showed no signs of cognitive impairment when they enrolled. Participants provided blood samples for p-tau217 analysis and underwent PET brain scans. During the study period, approximately 478 participants developed cognitive impairment.

For those with the highest p-tau217 levels, the estimated risk of cognitive impairment escalated to 78% within ten years. Researchers caution that this longer-term prediction is based on substantially fewer observations and is considered less certain. The biomarker provided predictive information beyond established risk factors like amyloid-beta plaques and the genetic risk factor APOE4.

The study combined insights from six separate observational studies and clinical trials. Data collection spanned follow-up periods from as early as 2004 to 2025. The research was led by scientists at the Mass General Brigham Neuroscience Institute, including lead author Rachel F. Buckley, PhD, and senior author Reisa Sperling, MD.

How the test works and its potential

The blood test measures levels of phosphorylated tau 217, a protein closely linked to Alzheimer's disease pathology. This test recently received federal clearance. The study suggests it could one day function similarly to cholesterol testing for heart disease, providing a quantifiable measure of future risk.

Its primary near-term application is expected in research, particularly for enrolling participants in prevention trials. As disease-modifying therapies continue to be developed and tested, the blood test could guide early intervention for eligible individuals long before overt symptoms emerge.

Study limitations and current recommendations

Researchers highlighted several important limitations. The study's participants may not fully represent the broader population, introducing potential selection bias. They strongly caution against using such blood tests for routine Alzheimer's risk screening in asymptomatic, healthy people. This is due to the current lack of approved preventive treatments.

Senior author Reisa Sperling stated that preventive care recommendations remain unchanged for now. Experts recommend maintaining a healthy lifestyle with regular exercise, good nutrition, and adequate sleep regardless of any test results. More extensive and diverse studies are needed to validate these findings and refine long-term risk predictions.

Funding and future steps

The study received partial funding from a mix of public and private organizations, including the National Institutes of Health, the U.S. Department of Defense, Eli Lilly, and the Alzheimer's Association. Additional authors on the paper include Diana L. Townsend and Colin J. Birkenbihl among others affiliated with Mass General Brigham and other institutions.

The future utility of the test hinges on the ongoing development of effective preventive therapies. For now, it represents a significant step toward identifying at-risk individuals who could benefit from early intervention in clinical trial settings.