Can a Blood Test Help Predict Alzheimer's Disease's Symptoms?

When trying to anticipate a diagnosis of Alzheimer’s disease, testing for the disease alone is only one factor to consider; there’s also a matter of predicting the onset of symptoms. The latter is where research into a type of protein called tau comes into play. As a 2025 dispatch from Stanford Medicine pointed out, tau what neurofibrillary tangles are composed of, and neurofibrillary tangles are one of two key components of Alzheimer’s disease.

Earlier this month, Nature Medicine published a paper that sought to determine how effective a blood test could be in anticipating the onset of Alzheimer’s symptoms. The paper’s authors note that while “clock models based on amyloid and tau positron emission tomography have shown promise in predicting the onset of AD symptoms, a model based on plasma biomarkers would be more accessible.”

The scientists doing this research found that the ratio of phosphorylated to non-phosphorylated tau at position 217 (“%p-tau217”) could predict the arrival of Alzheimer’s symptoms within three and four years. The authors write that this may “limit its utility for individual decision-making, but it could still be useful for group-level studies.”

These results also suggest that we aren’t quite at the point of an all-purpose Alzheimer’s-related blood test. Or, as Washington University School of Medicine’s Suzanne Schindler told Nature, “[W]e do not recommend that any cognitively unimpaired individuals have any Alzheimer’s disease biomarker test.”

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Why develop a blood-based test to begin with? Schindler told Nature that the current ways of searching for tau as a result of neurofibrillary tangles requires a significant amount of equipment; the idea of analyzing a blood sample is much less resource-dependent. There’s more work to do before this knowledge is ready for wider use, but it’s another step in better understanding a devastating disease.

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Tobias Carroll

Tobias Carroll lives and writes in New York City, and has been covering a wide variety of subjects — including (but not limited to) books, soccer and drinks — for many years. His writing has been published by the likes of the Los Angeles Times, Pitchfork, Literary Hub, Vulture, Punch, the New York Times and Men’s Journal. At InsideHook, he has…