Blood test measuring p-tau217 may forecast Alzheimer's risk up to a decade ahead
Researchers found that very high levels of the blood biomarker p-tau217 in cognitively normal older adults were linked to a 38% chance of cognitive impairment within five years and 78% within ten years, though experts caution the test is not yet ready for routine clinical use.
A study presented at the Alzheimer's Association International Conference in London reported that a blood test for the protein p-tau217 can identify older adults who are at elevated risk of developing Alzheimer's-related cognitive impairment over the next five to ten years. The analysis, published in JAMA, examined 2,684 participants who were symptom-free at enrollment and received the test along with annual cognitive assessments. Those with the highest p-tau217 concentrations faced a 38% risk of impairment within five years, rising to 78% after ten years, while individuals with low levels showed minimal risk.
The test, currently used to aid diagnosis in people with existing cognitive problems, measures a tau protein form that correlates with brain amyloid plaque burden and may signal the onset of neurofibrillary tangles. "This is a gradual process where amyloid and tau build up in the brain and this blood-based biomarker is telling you how far you are in that process," said Dr. Reisa Sperling, senior author of the study.
Researchers emphasized that the findings are not yet sufficient to recommend testing for healthy individuals. "Wait and get tested when you can potentially do something about it," Sperling added, recommending lifestyle measures such as a balanced diet, regular exercise, adequate sleep and mental engagement.
External experts praised the work but urged caution. Dr. Suzanne Schindler and Dr. David Wolk noted that only a small subset of participants had ten-year follow-up data, limiting confidence in long-term risk estimates, and that other health conditions could confound predictions. They wrote that the blood tests are "not yet precise enough to guide individualized prognosis," though they consider the study a valuable contribution to understanding disease progression.
Clinicians reported increasing public interest, with some patients requesting the test despite the lack of approved preventive treatments. Jessica Langbaum of the Banner Alzheimer’s Institute said she discourages such requests until an effective intervention becomes available.