Lexicon
pTau-217
Also known as p-tau, p-tau 217, phospho-tau
Definition
Plasma phosphorylated tau (p-tau) assays exhibit high diagnostic accuracy in distinguishing Alzheimer's disease from other neurodegenerative diseases in patients with cognitive impairment. [1] p-tau217 refers to tau phosphorylated at threonine 217, and it does not predict pathological changes in patients with other neurodegenerative disorders, making it specific to Alzheimer's disease. [2] Among blood-based biomarkers, phosphorylated tau217 is currently the most promising plasma biomarker to detect Alzheimer's disease pathology. [3]
How it works
Plasma p-tau217 has a close association with both brain amyloid-beta and tau pathology as well as a large dynamic range, which underlies its performance as a biomarker. [4] All p-tau isoforms increase as a function of amyloid-beta accumulation, with p-tau231 increasing earliest, followed by p-tau181 and p-tau217, and the greatest increase in advanced stages seen for p-tau217. [5]
Connected concepts
How it's measured
p-tau217 is measured in plasma with ultra-sensitive immunoassays or mass-spectrometry assays, offering a less invasive and more cost-effective alternative to cerebrospinal fluid sampling or positron emission tomography. [1] [4] Plasma p-tau217 is highly resistant to pre-analytical sample-handling variations, in contrast to plasma amyloid-beta 42 and 40 which are the most sensitive to such variations. [6] Many commercially available blood-biomarker tests do not meet recommended accuracy thresholds when using a single cutoff, and validation of optimal cutoffs for real-world clinical use is still needed. [7] [4]
What levels mean
In a meta-analysis of 113 studies comprising 29 625 individuals, plasma p-tau217 was the highest-performing biomarker for biologically defined Alzheimer's disease, with pooled sensitivity of 88·1%, specificity of 88·7% and area under the curve of 91·1%. [8]
Community knowledge
## Test Overview And Mechanism
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- 1.Hansson O, Blennow K, Zetterberg H, Dage J. Blood biomarkers for Alzheimer's disease in clinical practice and trials. Nat Aging · 2023
- 2.Telser J, Risch L, Saely CH, Grossmann K, Werner P. P-tau217 in Alzheimer's disease. Clin Chim Acta · 2022
- 3.Ottoy J, Owsicki N, Bilgel M, Binette AP, Salvadó G, Kang MS, Cash DM, Ewers M. Recent advances in neuroimaging of Alzheimer's disease and related dementias. Alzheimers Dement · 2025
- 4.Teunissen CE, Kolster R, Triana-Baltzer G, Janelidze S, Zetterberg H, Kolb HC. Plasma p-tau immunoassays in clinical research for Alzheimer's disease. Alzheimers Dement · 2025
- 5.Telser J, Grossmann K, Wohlwend N, Risch L, Saely CH, Werner P. Phosphorylated tau in Alzheimer's disease. Adv Clin Chem · 2023
- 6.Verberk IMW, Gouda M, Antwi-Berko D, van Leeuwenstijn M, Bongers B, Houtkamp IM, van der Flier WM, Janelidze S.
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