Blood Test Could Tell You When Alzheimer's Symptoms Will Start

Researchers say they're edging closer to a kind of countdown clock for Alzheimer's. A study published Thursday in Nature Medicine reports that a blood test tracking a protein called p-tau217 can estimate when someone is likely to develop symptoms, with a margin of about three to four years, per the Washington Post. A blood test reflecting buildup of amyloid plaques in the brain is already used in diagnosing people who have memory issues; this work, based on data from 600 older adults, pushes it into the realm of prediction, at least for research purposes. Higher levels of p-tau217 were tied to faster onset of symptoms, and age mattered: a spike at 60 was linked to symptoms about 20 years later, compared with 11 years if levels rose at 80.

The model isn't accurate enough yet for routine clinical use (though it could be improved by tracking other markers of disease in the blood), and the researchers stress it shouldn't be used on healthy people outside studies. But specialists say it could quickly reshape how trials are run by pinpointing symptom-free volunteers who are likely to decline soon—crucial if experimental drugs work best before noticeable memory loss. "Eventually, the goal is to be able to tell individual patients when they are likely to develop symptoms," senior author Dr. Suzanne Schindler of Washington University says in a release. Experts not involved in the study call the approach promising but say it must be validated in larger, more diverse groups and will only be truly useful if early, risk-balancing treatments prove effective.