Blood Test Shows Potential in Predicting Alzheimer’s Risk

A recent study suggests that a blood test measuring a single protein may predict a person’s risk of developing Alzheimer’s-related cognitive decline up to a decade before symptoms appear. This research, presented at the Alzheimer’s Association International Conference 2026 in London, focuses on the biomarker p-tau217, linked to a 78% risk of cognitive impairment over ten years for those with high levels but no initial symptoms.

Alzheimer’s Impact in the U.S.

Currently, nearly 7 million Americans live with Alzheimer’s disease. This figure is expected to nearly double to approximately 13 million by 2050, as reported by the Alzheimer’s Association, unless significant medical progress is made.

Promise and Cautions of the Test

Dr. Manisha Parulekar from Hackensack University Medical Center highlighted the test’s potential to transform Alzheimer’s risk assessment. She suggested this could shift the focus from specialty clinics to primary care, allowing earlier interventions that target factors like blood pressure and physical activity. This could facilitate recruitment for prevention trials to determine if intervening early may delay disease onset.

However, Dr. Parulekar warned about the risks associated with a positive test result, including psychological distress and insurance discrimination. She emphasized the need for responsible implementation with structured counseling and equitable access to resources.

Details of the Study

The study analyzed blood samples from nearly 2,700 cognitively healthy adults, average age 70, from major Alzheimer’s research groups and clinical trials. It is among the largest studies of its kind, with participants followed for almost five years, up to over a decade. Results indicated adults with p-tau217 levels more than double the average faced a 78% risk of impairment in ten years; the risk was reduced to 15% over five years and 45% over ten years for those with moderately elevated levels.

The p-tau217 protein is a modified tau form and a hallmark of Alzheimer’s disease, forming tangles in the brain and closely tied to cognitive decline. The blood test adds predictive value beyond brain scans and genetic testing.

Ongoing Research and Considerations

Rachel F. Buckley from the Mass General Brigham Neuroscience Institute noted the test offers significant evidence for detecting dementia risk earlier in patients without symptoms. This could assist in trials for treatments to prevent decline. However, researchers indicate that the biomarker alone does not predict individual risk completely. Factors like age, genetics, and diverse backgrounds affect biomarker levels. Diverse study populations and longer follow-up are necessary for refining risk estimates.

The FDA approved the use of the p-tau217 blood test in the United States. In May 2025, the FDA cleared Fujirebio’s Lumipulse G pTau217/β-Amyloid 1-42 Plasma Ratio as the first in vitro diagnostic blood test to aid in diagnosing Alzheimer’s disease.

“Some of the clearest evidence yet that elevated p-tau217 levels may help detect dementia risk years earlier—even in adults with no noticeable memory or thinking problems.” — Rachel F. Buckley