A simple blood test may enable much earlier detection of Alzheimer’s disease than previously thought. Researchers from Mass General Brigham have shown that the biomarker plasma phosphorylated tau 217 (pTau217) can predict disease progression years before abnormalities appear on brain scans or symptoms emerge.
“PET scans were long considered the earliest indicator of Alzheimer’s, detecting amyloid buildup up to two decades before symptoms,” said lead author Hyun-Sik Yang. “Our results show that pTau217 becomes detectable even earlier, before PET scans reveal clear abnormalities.” The findings, published in Nature Communications, suggest that blood-based biomarkers could shift Alzheimer’s diagnostics from reactive to proactive, identifying at-risk individuals at a much earlier stage.
Predictive value
The study followed 317 cognitively healthy adults, aged 50 to 90, as part of the Harvard Aging Brain Study over an average of eight years. Participants underwent repeated blood testing, amyloid and tau PET scans, and cognitive assessments.
Researchers found that elevated levels of pTau217 were strongly associated with faster accumulation of Alzheimer’s-related pathology, including amyloid plaques and tau tangles. Notably, increases in pTau217 often preceded detectable changes on PET scans, highlighting its value as an early warning signal.
Conversely, participants with low baseline levels of the biomarker were unlikely to develop significant amyloid buildup over the study period. This dual predictive capability, identifying both high- and low-risk individuals, could prove critical for future screening strategies.
Accessible and scalable diagnostics
The results build on recent momentum in blood-based Alzheimer’s diagnostics, following regulatory clearance of the first such test in the United States. Compared to traditional methods like PET imaging or lumbar punctures, blood tests are less invasive, more affordable and easier to scale.
According to co-author Jasmeer Chhatwal, the ability to anticipate who will develop amyloid pathology opens new opportunities for early intervention and prevention. “By identifying individuals at risk earlier, we can potentially intervene before significant brain damage occurs,” he noted.
While the researchers caution that pTau217 testing is not yet ready for routine clinical use, they see strong potential for application in clinical trials. Early identification of at-risk individuals could improve participant selection and accelerate the development of preventive therapies.
Shifting Alzheimer’s care
As Alzheimer’s research increasingly focuses on early-stage intervention, tools that detect disease before clinical symptoms emerge are becoming essential. Blood-based biomarkers like pTau217 could play a central role in this transition, enabling routine screening and longitudinal monitoring in broader populations.
The study underscores a broader trend in healthcare: moving diagnostics closer to patients while improving predictive accuracy. If validated in larger and more diverse populations, blood tests for Alzheimer’s could become a cornerstone of preventive neurology, offering a more patient-friendly alternative to current imaging-based approaches. Ultimately, the ability to detect Alzheimer’s risk years in advance may not only improve individual outcomes but also help healthcare systems better manage the growing burden of neurodegenerative disease.
Similar blood test
Last year, researchers at the Mayo Clinic developed a new blood test that offers a promising, non-invasive approach to early Alzheimer’s diagnosis. Published in Alzheimer's & Dementia, the study shows the test can detect Alzheimer’s in patients with cognitive impairment with up to 95% accuracy in outpatient settings. The test measures key biomarkers in blood plasma, including Aβ42/40 and p-tau217, both linked to amyloid plaque formation. The p-tau217 marker proved particularly reliable.
Tested in over 500 patients with various cognitive disorders, the method provides a simpler and more affordable alternative to PET scans and spinal taps. Researchers highlight its potential not only for routine clinical care but also for improving patient selection and monitoring in clinical trials, supporting earlier and more accessible dementia diagnostics.
