Blood Test Breakthrough: Early Alzheimer’s Detection Years Before Symptoms Emerge

A blood test for the biomarker pTau217 can predict Alzheimer’s disease progression years before symptoms appear or brain scan changes are detectable, according to new research from Mass General Brigham and Harvard-affiliated investigators.

The study, published in Nature Communications, followed 317 cognitively healthy older adults from the Harvard Aging Brain Study for an average of eight years. Participants, aged 50 to 90, underwent blood tests for pTau217, repeated amyloid and tau PET scans and long-term cognitive testing.

Researchers found that higher levels of pTau217 predicted a faster buildup 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 previously thought possible.

Lead author Hyun-Sik Yang, MD, a neurologist with Mass General Brigham Neuroscience Institute and an associate member of the Broad Institute of MIT and Harvard, stated that while PET scan detection was once considered the earliest sign of Alzheimer’s disease progression—revealing amyloid accumulation 10 to 20 years before symptoms—pTau217 can now be detected years earlier, well before clear abnormalities appear on amyloid PET scans.

Last year, the U.S. Food and Drug Administration cleared the first blood test for Alzheimer’s disease, providing a cheaper, less invasive alternative to lumbar punctures and PET scans. The new study adds important evidence about the predictive potential of these blood tests for identifying individuals at risk for cognitive decline.

The findings may help push back the clock to enable simpler, earlier disease prediction and indicate who may be at risk for future cognitive decline. Researchers suggest that such tests could aid in selecting participants for clinical trials aimed at preventing symptom development.