Plasma p-tau217
The most specific blood biomarker for Alzheimer's disease pathology
Phosphorylated tau at threonine-217 (p-tau217) is a protein released into the blood when the brain develops Alzheimer's-type tau tangles and amyloid plaques. It is the most specific plasma biomarker currently available for identifying Alzheimer's disease pathology. A single p-tau217 blood test can predict amyloid PET positivity with an accuracy of ~94%, comparable to a brain scan.
Adults aged ≥50 with cognitive symptoms or MCI undergoing evaluation for Alzheimer's disease. Clinicians initiating or monitoring anti-amyloid therapy (lecanemab, donanemab). Specialist memory clinics requiring biomarker-confirmed AD diagnosis.
Not for asymptomatic general population screening. Requires specialist clinical interpretation. Not validated as a standalone test without clinical assessment.
Plasma phosphorylated tau at threonine-217 (p-tau217)
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.
Samples must be collected and submitted by a licensed healthcare professional.
- Store samples at 4°C (refrigerator) for up to 6 hours after collection.
- Samples must be ready for pick-up by 15:00 on weekdays.
- Pick-up service is not available on public holidays.
- Contact Codex Genetics to arrange pick-up: Tel +852 3008 2560 / WhatsApp +852 9837 1345. Address: Unit 220, 2/F, Building 16W, HKSTP, Pak Shek Kok, NT, Hong Kong.
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.
Per the NIA-AA 2024 revised criteria (Jack CR Jr et al., Alzheimer's & Dementia 2024; DOI: 10.1002/alz.13859), plasma p-tau217 is classified as a Core Tier 1 biomarker — the highest evidence tier — for Alzheimer's disease diagnosis. Multiple large independent studies have demonstrated AUC 0.92–0.96 against amyloid PET concordance. Elevated p-tau217 indicates both amyloid plaque burden (A) and tau pathology (T) in the AT(N) framework. It outperforms p-tau181 and Aβ42/40 as a standalone biomarker in most head-to-head comparisons. The 2024 NIA-AA criteria establish that a clearly abnormal p-tau217 result is sufficient to diagnose Alzheimer's pathological change in symptomatic individuals.
Hong Kong-based molecular diagnostics laboratory specialising in clinical genomics, precision oncology, and rare disease diagnosis. Accredited to ISO 27001 and GenQA standards.
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