A blood test for the biomarker phosphorylated tau 217 (p-tau217) recently received federal clearance, but questions have emerged about the extent to which such tests can accurately predict whether a cognitively healthy individual will develop cognitive impairment—a key symptom of Alzheimer’s disease.

A new international study involving researchers across three continents and led by experts from the Mass General Brigham Neuroscience Institute sheds new light on the prognostic value of such tests.

The study found that cognitively unimpaired individuals with very high levels of the biomarker had a 38% absolute risk of developing cognitive impairment over the next five years and a 78% risk over the next 10 years.