A blood test measuring plasma phosphorylated tau 217 (pTau217) can predict Alzheimer’s disease progression years before abnormalities appear on brain scans, according to a study from Mass General Brigham published in Nature Communications.
The prospective cohort study followed 317 cognitively healthy older adults from the Harvard Aging Brain Study for an average of eight years. Participants, aged 50 to 90 years, underwent blood tests for pTau217, repeated amyloid and tau PET scans, and long-term cognitive testing.
Researchers found that higher pTau217 levels predicted faster accumulation of Alzheimer’s disease pathology, even when initial brain scans appeared normal. Increases in pTau217 frequently occurred before amyloid PET scans became positive, highlighting the biomarker’s ability to detect changes earlier than current imaging methods.
Importantly, participants with low pTau217 levels at baseline were very unlikely to accumulate significant amyloid-beta on their PET scans over many years of follow-up, suggesting the test could identify individuals who will remain at low risk.
Lead author Dr Hyun-Sik Yang, a neurologist with Mass General Brigham Neuroscience Institute, noted that PET scan detection was previously considered the earliest sign of Alzheimer’s progression, revealing amyloid accumulation 10 to 20 years before symptoms appear. The new findings suggest pTau217 can be detected even earlier.
Last year, the US Food and Drug Administration cleared the first blood test for Alzheimer’s disease, offering a cheaper, less invasive alternative to lumbar punctures and PET scans. Whilst routine pTau217 testing is not yet recommended, researchers hope it will serve as a scalable screening tool for clinical trials targeting Alzheimer’s prevention and help identify higher-risk individuals.
Source: Medical Xpress / Mass General Brigham (Nature Communications, 2026)
The prospective cohort study followed 317 cognitively healthy older adults from the Harvard Aging Brain Study for an average of eight years. Participants, aged 50 to 90 years, underwent blood tests for pTau217, repeated amyloid and tau PET scans, and long-term cognitive testing.
Researchers found that higher pTau217 levels predicted faster accumulation of Alzheimer’s disease pathology, even when initial brain scans appeared normal. Increases in pTau217 frequently occurred before amyloid PET scans became positive, highlighting the biomarker’s ability to detect changes earlier than current imaging methods.
Importantly, participants with low pTau217 levels at baseline were very unlikely to accumulate significant amyloid-beta on their PET scans over many years of follow-up, suggesting the test could identify individuals who will remain at low risk.
Lead author Dr Hyun-Sik Yang, a neurologist with Mass General Brigham Neuroscience Institute, noted that PET scan detection was previously considered the earliest sign of Alzheimer’s progression, revealing amyloid accumulation 10 to 20 years before symptoms appear. The new findings suggest pTau217 can be detected even earlier.
Last year, the US Food and Drug Administration cleared the first blood test for Alzheimer’s disease, offering a cheaper, less invasive alternative to lumbar punctures and PET scans. Whilst routine pTau217 testing is not yet recommended, researchers hope it will serve as a scalable screening tool for clinical trials targeting Alzheimer’s prevention and help identify higher-risk individuals.
Source: Medical Xpress / Mass General Brigham (Nature Communications, 2026)
