Plasma p-tau217

The Plasma p-Tau217 assay quantifies phosphorylated tau at threonine 217, currently the most accurate blood biomarker of underlying Alzheimer's disease pathology. Ultra-sensitive immunoassay platforms reliably measure this isoform in plasma and detect amyloid PET-positive individuals with AUCs of 0.93–0.96 in clinical validation studies. p-Tau217 rises earlier and with greater fold-change than other plasma tau isoforms, supporting both screening and triage for disease-modifying therapy eligibility.

1. Detecting Alzheimer's disease pathology in patients with mild cognitive impairment or dementia.
2. Triaging the need for amyloid PET or CSF biomarker testing, substantially reducing lumbar punctures in memory-clinic settings.
3. Supporting eligibility assessment for anti-amyloid monoclonal-antibody therapy.
4. Risk stratification in cognitively unimpaired individuals with a family history of Alzheimer's disease.

Use 2x EDTA vacuum blood collection tubes (purple cap) to draw 4 mL of venous blood.

Transfer to 4°C for immediate storage and arrange shipment to Codex Genetics Laboratory (within 6 hours)

Available through Codex Genetics as part of the Neurodegenerative Biomarker panel. Please contact us for requisition forms and shipping instructions.

Reported as continuous pg/mL with interpretive cut-offs for amyloid PET concordance. Results classified as: Positive (elevated, consistent with AD pathology) / Intermediate / Negative.

Elevated plasma p-tau217 is consistent with Alzheimer's amyloid and tau pathology. Results should be interpreted in the context of clinical symptoms, APOE genotype, and other biomarkers. A clearly positive result in a symptomatic patient supports an AD diagnosis per NIA-AA 2024 criteria.

Phosphorylated tau at threonine 217 is more specific to Alzheimer's disease pathology than p-Tau181 and shows the largest fold-change between Alzheimer-positive and Alzheimer-negative individuals of the established plasma tau isoforms. In prospective clinical validation cohorts, plasma p-Tau217 has detected amyloid PET positivity with AUCs of 0.93–0.96, and combined p-Tau217/Aβ42 ratios have achieved AUCs approaching 0.97 against amyloid and tau PET. Reported sensitivity and specificity in memory-clinic cohorts range from 81–95% and 91–96% at standard cut-offs, and a two-cut-off strategy with 95% sensitivity and specificity can avoid an estimated 65% of lumbar punctures. With anti-amyloid therapies now approved for early Alzheimer's disease, plasma p-Tau217 is positioned as the leading blood biomarker for pre-screening and triage.