Phosphorylated Tau 217 (P Tau 217) is a biomarker relevant to neurodegenerative disease diagnosis and research. This page provides detailed information about its characteristics, detection methods, and clinical significance.
Phosphorylated tau at threonine 217 (p-tau217) is one of the most promising blood-based biomarkers for detecting Alzheimer's disease (AD) pathology in vivo.[1][2] As a phosphorylation-specific fragment of the microtubule-associated protein tau, p-tau217 reflects the pathological accumulation of neurofibrillary tangles (NFTs) in the brain with high specificity.[3] Unlike total tau measurements, p-tau217 specifically captures the disease-associated phosphorylation state that drives neurodegeneration in AD and related tauopathies.[4]
The development of ultra-sensitive immunoassays capable of detecting p-tau217 in plasma has revolutionized Alzheimer's disease biomarker research, enabling large-scale screening and early detection initiatives that were previously impossible with cerebrospinal fluid (CSF) or PET imaging approaches.[5]
Tau is a microtubule-associated protein encoded by the MAPT gene that stabilizes microtubules in neuronal axons.[6] In AD and other tauopathies, tau becomes abnormally hyperphosphorylated, leading to its aggregation into paired helical filaments (PHFs) that form neurofibrillary tangles.[7] The tau protein has 85 potential phosphorylation sites across multiple isoforms generated by alternative splicing. Phosphorylation at threonine 217 occurs in the proline-rich region of tau, adjacent to multiple kinases including glycogen synthase kinase 3β (GSK-3β), cyclin-dependent kinase 5 (CDK5), and casein kinases.[8]
The phosphorylation at T217 is particularly relevant because it:
Multiple pharmaceutical and research groups have developed highly sensitive immunoassays for plasma p-tau217, including Simoa-based platforms and Elecsys systems.[1][2] These assays achieve detection limits in the femtomolar range, making plasma measurement feasible for clinical research and eventually clinical practice.[5]
P-tau217 has demonstrated exceptional diagnostic accuracy for AD, with AUC values ranging from 0.89 to 0.98 depending on the comparison group.[1][2][3] Studies show sensitivity of 85-96% and specificity of 84-92% for distinguishing AD from cognitively normal individuals and other neurodegenerative disorders.[1][4]
P-tau217 shows strong correlation with established AD biomarkers:
P-tau217 can help identify disease stage:[2][10]
Both p-tau217 and p-tau181 are FDA-approved plasma biomarkers, but they show differences:[4][5]
Plasma p-tau217 correlates well with CSF p-tau217 (r = 0.75-0.85), but plasma offers less invasive collection, broader clinical applicability, feasibility for repeated sampling, and cost-effective screening.[5]
Proper sample handling is critical for accurate measurement:
Interpretation should consider:[11][12]
P-tau217 shows promise for monitoring treatment response in clinical trials:[13][14]
The study of Phosphorylated Tau 217 (P Tau 217) has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
Palmqvist S, Janelidze S, Quiroz YT, et al. Discriminatory accuracy of plasma phospho-tau217 for Alzheimer disease vs other neurodegenerative disorders. JAMA. 2020;324(8):772-781.
Janelidze S, Teunissen CE, Zetterberg H, et al. Head-to-head comparison of 8 plasma amyloid-beta 42/40 and phospho-tau assays in Alzheimer disease. JAMA Neurology. 2021;78(11):1375-1382.
Karikari TK, Pascoal TA, Ashton NJ, et al. Blood phosphorylated tau 217 ties to tell tau pathology in Alzheimer disease. Nature Medicine. 2022;28(9):1827-1834.
Ashton NJ, Pascoal TA, Karikari TK, et al. Plasma p-tau231: a new biomarker for incipient Alzheimer's disease pathology. Nature Medicine. 2021;27(12):2127-2135.
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Pontecorvo MJ, Devous MD, Kennedy I, et al. A multicentre longitudinal study of flortaucipir (18F-AV-1451) in autosomal dominant Alzheimer's disease. Brain. 2019;142(9):2803-2817.
Mattsson-Carlgren N, Salvadó G, Ashton NJ, et al. Prediction of longitudinal progression in sporadic Alzheimer's disease using plasma biomarkers. JAMA Neurology. 2023;80(4):360-370.
Blennow K, Zetterberg H. The past and future of Alzheimer's disease fluid biomarkers. JAMA Neurology. 2023;80(1):5-6.
Scheltens P, De Strooper B, Kivipeldo M, et al. Alzheimer's disease. Lancet. 2021;397(10284):1577-1590.
Sims JR, Zimmer JA, Evans CD, et al. Lecanemab in early Alzheimer's disease. New England Journal of Medicine. 2023;388(1):9-21.
Cummings JL, Tong G, Ballard C. Treatment combinations for Alzheimer's disease: current and future pharmacotherapy options. Alzheimer's & Dementia: Translational Research & Clinical Interventions. 2019;5(1):364-382.