A straightforward blood test might soon revolutionize how doctors spot individuals with a high chance of future Alzheimer’s disease. New research indicates that a few blood biomarkers may identify clues years before people show potential symptoms, or before clear alterations appear in brain scans.
Scientists have been investigating phosphorylated tau 217 (p-tau217 for short), an indicator of Alzheimer’s disease brain changes. Preliminary data shared at the 2026 Alzheimer’s Association International Conference (AAIC) indicate that the levels of p-tau217 in blood samples taken from an individual with no apparent memory problems can give insight into future levels of cognitive decline.
The study looked at close to 2,700 healthy adults averaging 70 years old and older. They were tracked for a number of years as blood-based biomarkers were measured plus other measures of Alzheimer’srelated pathology and cognitive function. The researchers were not interested in knowing if the individual already has the disease, but whether the blood test might tell us what may happen a few years down the road.
The findings were striking. Individuals with extremely high levels of p-tau217 averaged a 78% chance of going on to develop cognitive impairment within 10 years. Their average five-year risk was approximately 38%. Those with high, but not as high, levels of the biomarkers had a significant risk, but not nearly as high as the group with the most extreme biomarker levels.
The reason the results have gained so much attention is because blood testing is much less invasive and more accessible against the high-tech brain scans. While it is possible to detect pain and before it can exist in the brain with a PET scan, this kind of scan is costly and not always available.
Previous studies show that p-tau217 may be most of all accurate in the diagnosis of Alzheimer’s pathology. In 2024, published in Nature Medicine, a study showed that plasma p-tau217 as good as, or better than, current CSF tests for amyloid and tau pathology, in a sample of cognitively impaired individuals.
The most recent studies make an additional contribution though in that they suggest the biomarker could be used to predict. Rather than just showing the presence or absence of Alzheimer’s pathology, p-tau217 levels may allow researchers to estimate the probability of subsequent decline. This would be mostly useful in clinical trials, in which identifying individuals who will probably decline could inform the testing of preventative therapies.
Meanwhile, the researcher warned against viewing the blood test as a fortune teller. The p-tau217 result can’t tell if or precisely when someone will get Alzheimer’s. Scientists observed that attributes such as age, genetics, and renal health could affect the biomarker readings as well as the overall dementia risk. Further study in more diverse populations and for a longer time frame is necessary.
A further potential direction of research is to look outside of p-tau217 entirely. A recent study funded by the National Institute of health found 34 circular RNAs in blood that were linked to Alzheimer’s disease.
