Brain Health

Blood Test for Alzheimer's Risk Identifies Disease Decades Before Symptoms

A large multi-cohort study published in JAMA Neurology found that a simple blood test measuring phosphorylated tau 217 (p-tau217) can reliably identify cognitively normal adults who have Alzheimer's disease pathology in the brain — years or even decades before any memory symptoms appear. Across more than 1,700 participants from eight international cohorts, p-tau217 showed strong agreement with amyloid and tau PET scans, the current gold standard for detecting preclinical Alzheimer's. The test achieved over 85% accuracy in identifying amyloid-positive individuals, suggesting it could serve as a scalable, low-cost screening tool for clinical trials and eventually routine clinical care.