Plasma p-tau181
Validated plasma biomarker for early Alzheimer's disease tau pathology
Plasma p-tau181 measures phosphorylated tau protein at threonine-181 in the blood. It was the first plasma tau biomarker to be widely adopted in clinical and research settings and remains a core tool for Alzheimer's disease evaluation. It is classified as a Core Tier 2 biomarker by the NIA-AA 2024 criteria.
Evaluation of symptomatic patients for Alzheimer's disease pathology. Longitudinal biomarker monitoring in known AD patients. Research and clinical trial screening for amyloid/tau positivity.
Not for asymptomatic screening. Not a standalone diagnostic without clinical context.
Plasma phosphorylated tau at threonine-181 (p-tau181)
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. Please contact us for collection kits and requisition forms.
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 in pg/mL relative to validated amyloid PET concordance cut-offs.
Elevated p-tau181 is consistent with Alzheimer's tau pathology. Interpret alongside clinical assessment and other NIA-AA 2024 biomarkers for full AT(N) staging.
Per the NIA-AA 2024 revised criteria (Jack CR Jr et al., Alzheimer's & Dementia 2024; DOI: 10.1002/alz.13859), plasma p-tau181 is a Core Tier 2 biomarker for Alzheimer's disease. It demonstrates good concordance with tau PET and amyloid PET (AUC 0.85–0.90 in most studies). While slightly less discriminating than p-tau217 in head-to-head comparisons, it remains a validated and widely available option. p-tau181 rises early in the AD continuum, making it useful for preclinical and prodromal disease detection.
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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