Blood Tests Could Revolutionize Early Alzheimer’s Detection and Risk Prediction, New Studies Show

A new study has found that a blood test measuring levels of phosphorylated tau 217 (pTau217) can predict the progression of Alzheimer’s disease years before symptoms appear or changes are visible on brain scans. This development could simplify early detection and help identify individuals at risk for cognitive decline long before traditional methods.

The research, conducted by investigators at Mass General Brigham and affiliated with Harvard Medical School, followed 317 cognitively healthy adults aged 50 to 90 from the Harvard Aging Brain Study for an average of eight years. Participants underwent regular blood tests for pTau217, repeated amyloid and tau PET scans and long-term cognitive assessments. The study found that higher baseline levels of pTau217 predicted a faster accumulation of Alzheimer’s pathology, even when initial brain scans showed no abnormalities.

Lead author Hyun-Sik Yang, an assistant professor of neurology at Harvard Medical School and Brigham and Women’s Hospital, noted that while PET scans were previously considered the earliest sign of Alzheimer’s—revealing amyloid buildup 10 to 20 years before symptoms—pTau217 can now be detected years earlier, well before clear abnormalities appear on amyloid PET scans.

The findings, published in Nature Communications, add to growing evidence supporting blood-based biomarkers as a less invasive and more accessible alternative to lumbar punctures and expensive imaging. Last year, the U.S. Food and Drug Administration cleared the first blood test for Alzheimer’s disease, paving the way for broader clinical use of such tools.