Plasma p-tau217 proves highly accurate for diagnosing Alzheimer's across disease stages

A study in Annals of Neurology demonstrates that plasma p-tau217 and its ratio to amyloid-beta 42 provide excellent diagnostic accuracy for Alzheimer's disease, both in cross-sectional assessment and when tracking disease progression longitudinally. This blood-based biomarker performed well across different disease stages, from preclinical to dementia. The research is important because current Alzheimer's diagnosis relies on expensive PET scans or invasive lumbar punctures to measure brain amyloid and tau. A simple blood test that matches their accuracy could revolutionize screening and monitoring, making diagnosis accessible in primary care settings rather than specialized centers. The longitudinal performance is particularly valuable—the test can track disease progression over time, helping clinicians monitor both natural decline and treatment responses. With new amyloid-clearing drugs now approved, accessible biomarkers for patient selection and monitoring are crucial. The p-tau217/Aβ42 ratio showed especially strong performance, suggesting combination markers may be optimal. However, standardization across laboratories and real-world validation in diverse populations remain necessary steps before widespread clinical adoption.