Researchers at Mass General Brigham have discovered that a blood test measuring the biomarker pTau217 can predict the progression of Alzheimer’s disease years before symptoms appear or brain scans show physical changes.
The study, published in Nature Communications, suggests that measuring plasma phosphorylated tau 217 (pTau217) allows doctors to identify cognitively healthy adults at risk of future decline.
Previously, medical professionals relied on amyloid PET scans to detect the earliest signs of the disease, which typically reveal amyloid accumulation 10 to 20 years before symptoms manifest.
“But now we are seeing that pTau217 can be detected years earlier, well before clear abnormalities appear on amyloid PET scans,” said lead author Dr. Hyun-Sik Yang, a neurologist with the Mass General Brigham Neuroscience Institute.
Predictive power of pTau217
The prospective study tracked 317 cognitively healthy adults from the Harvard Aging Brain Study for an average of eight years. Participants, aged 50 to 90, underwent regular blood tests, PET scans, and cognitive assessments.
Researchers found that higher levels of pTau217 predicted a faster buildup of Alzheimer's pathology, even in patients whose initial brain scans appeared normal.
Increases in the biomarker frequently preceded positive amyloid PET scans. Conversely, participants with low pTau217 levels were unlikely to develop significant amyloid-beta accumulation during the follow-up period.
“What stood out in our study is that even when amyloid scans appear normal in the clinic, the pTau217 biomarker can identify individuals who later become amyloid-positive,” Yang said.
While the FDA cleared the first Alzheimer's blood test last year, this new evidence reinforces the potential for these tests to serve as a cheaper, less invasive alternative to lumbar punctures and expensive PET imaging.
Dr. Jasmeer Chhatwal, a co-senior author of the study, noted that the ability to anticipate which patients will become amyloid-positive is a vital step in clinical application.
Though researchers are not yet recommending routine pTau217 testing for all older adults, the team hopes the test will become a scalable screening tool for clinical trials and future routine health maintenance.