Plasma p-tau217 levels predict amyloid-beta positivity in the brain with 95% to 97% accuracy, enabling detection of Alzheimer's pathology decades before symptom onset.

Study: Multicenter validation of plasma p‐tau217/ amyloid beta 1‐42 ratio in symptomatic Alzheimer's disease

This blood test correctly identified almost all people who had Alzheimer’s plaques in their brain — it was right 97.6% of the time when plaques were present. While it doesn’t prove it works decades before symptoms, it shows the test is very accurate in people already showing memory problems.

Study: Diagnostic performance of plasma p-tau217 levels measured with different assays for Alzheimer’s disease

This study found that a simple blood test for p-tau217 can spot Alzheimer’s disease in the brain with very high accuracy — even in people with mild memory problems — and rarely gives false alarms. It’s like a smoke detector that almost always goes off when there’s a fire, and almost never when there isn’t.

Study: Clinical utility of plasma p‐tau217 in identifying abnormal brain amyloid burden in an Asian cohort with high prevalence of concomitant cerebrovascular disease

The study shows that a blood test for p-tau217 can help detect Alzheimer's plaques, but it’s only about 82% accurate—not 95% to 97% as the claim says. So the claim overstates how good the test is.

Study: Diagnostic Accuracy of Plasma p-tau217 as a Pre-Screening Tool for Amyloid-PET: A Decision Curve Analysis in the ADNI Cohort

This blood test can tell if someone likely has Alzheimer's plaques in the brain, but it's not quite as accurate as the claim says — it's about 95% good at ruling out plaques, not 95–97% accurate overall.