Can a blood test detect Alzheimer’s early?
A blood marker may flag Alzheimer’s years earlier than scans
Researchers at Mass General Brigham report progress toward detecting Alzheimer’s disease at its earliest, pre-symptomatic stages using a blood-based biomarker. The approach centers on a specific protein biomarker called pTau217 (phosphorylated tau 217).
The study used long-term data—meaning information was collected over time from individuals before clinical symptoms became obvious—and evaluated how well the blood test performed compared with brain imaging. The headline result is that the blood marker helped identify the earliest signs of Alzheimer’s in people who were still considered cognitively healthy, at a stage when traditional assessments may not yet show clear changes.
Why this matters
- Earlier detection could change treatment timing. Many Alzheimer’s interventions are most likely to help before significant brain changes take hold.
- Blood tests are scalable. Imaging-based detection is often expensive and less widely available than routine blood work.
- pTau217 is a molecular readout of tau pathology. Tau-related changes are central to Alzheimer’s disease biology, so measuring tau in blood aims to capture the process earlier and more conveniently.
What’s clear from the report
- The biomarker is pTau217.
- The work focuses on identifying earliest signs in cognitively healthy individuals.
- The comparison point is that brain scans show signs later, suggesting the blood test may lead.
What remains uncertain
The story excerpt doesn’t provide key performance details such as sensitivity/specificity or how results vary by age or risk factors. Additional data would be needed to understand how the test would be implemented in routine clinical screening.
Overall, the findings support the idea that tau biomarkers in blood can provide a practical window into Alzheimer’s disease before imaging detects overt changes.