Mass spectrometry analysis of plasma phosphorylated tau-217 (%p-tau217) demonstrates comparable predictive power to expensive brain PET scans for identifying individuals who will develop tau pathology within four years. Among 255 cognitively normal adults, those with higher %p-tau217 levels showed 52% increased risk of converting from tau-negative to tau-positive brain scans, with hazard ratios nearly matching amyloid-PET imaging performance.
This convergence represents a potential paradigm shift toward accessible blood-based Alzheimer's screening. Current tau-PET scans cost thousands of dollars and require specialized facilities, while plasma biomarkers could enable routine monitoring in standard clinical settings. The finding builds on emerging evidence that peripheral tau species reflect central nervous system pathology earlier than previously recognized. However, the 14.5% conversion rate over nearly four years suggests most at-risk individuals remain in preclinical stages longer than anticipated. The validation across two independent cohorts strengthens confidence, though longer follow-up periods and diverse populations will determine whether plasma tau can reliably stratify risk decades before symptom onset, ultimately enabling preventive interventions.
