New Blood Test May Predict Alzheimer's Risk

Older adults without cognitive impairment but with elevated levels of a blood biomarker called p-tau217 face a nearly 38% higher risk of developing early dementia signs within five years, according to new research. Over a decade, this risk escalates to 78%, though this longer-term data is less certain.

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This tells us that in the future, we will be able to use blood tests that measure p-tau217 to assess an individual's risk of developing cognitive disorders.

"This tells us that in the future, we will be able to use blood tests that measure p-tau217 to assess an individual's risk of developing cognitive disorders," said lead author Rachel Buckley, an associate professor of neurology at Harvard Medical School. Until now, diagnosing Alzheimer's disease typically required expensive and invasive procedures like PET brain scans or lumbar punctures.

However, blood tests measuring phosphorylated tau protein 217 (p-tau217) can reliably indicate the buildup of beta-amyloid plaques in the brain. These plaques trigger inflammation and disrupt neuronal communication, beginning decades before memory issues or other cognitive problems manifest. As amyloid increases, tau proteins also accumulate, forming tangles that lead to neuron degeneration.

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We believe that the p-tau217 test can show us the moment when amyloid begins to cause that process.

Buckley stressed that high levels of amyloid or tau alone do not guarantee dementia. However, she believes the p-tau217 test can signal when amyloid begins to drive the disease's spread through the brain. Experts emphasize that these tests are not currently recommended for healthy individuals but could be valuable for those with mild cognitive impairment or advanced dementia, potentially functioning like risk assessments for diabetes or heart attacks.

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I would never order just a p-tau217 test. It only shows one piece of a complex biological picture.