Aug 2026· Molecular Psychiatry· 0 citations· 35 references
Medicine
TL;DR
CSF p-tau205 as a biomarker of Alzheimer's disease pathology and progression with potential value for biological staging is supported and when incorporated into a conceptual CSF-based staging model, the final p-tau205-positive stage showed the strongest association with cortical atrophy, cognitive impairment, and risk of progression to dementia.
Abstract
Among soluble tau biomarkers, tau phosphorylation at position T205 (p-tau205) has been suggested to distinctly emergence across Alzheimer's disease (AD) continuum compared to other p-tau and non-phosphorylated tau forms, and a moderate relationship with both amyloid-β and tau aggregated pathologies. To evaluate this and further expand the characterization of this biomarker, we measured cerebrospinal fluid (CSF) p-tau205 using an in-house developed immunoassay in a total of 2069 samples from the BioFINDER-2 (n = 1364) and BioFINDER-1 (n = 705) cohorts. These two cohorts spanned the full AD continuum and were analyzed to assess cross-sectional and longitudinal associations with imaging and clinical measures. CSF p-tau205 levels were elevated in both biologically and clinically advanced disease stages. In Aβ-positive individuals, baseline p-tau205 levels correlated with Aβ-PET (R² = 0.28), tau-PET (medial temporal: R2 = 0.35, neocortical: R² = 0.29), cortical atrophy (R² = 0.15) and cognition (MMSE, R² = 0.15). Baseline p-tau205 predicted subsequent Aβ accumulation (R² = 0.44) and tau-accumulation measured by PET (R² = 0.33). Longitudinal p-tau205 levels increased more steeply longitudinally in Aβ-positive than Aβ-negative participants (β[95%CI] = 0.16[0.12-0.21], p < 0.001). Longitudinal p-tau205 changes were associated with cortical thinning (R² = 0.32) and cognitive decline (R² ≥ 0.41). When incorporating Aβ42/40, p-tau217 and p-tau205 into a conceptual CSF-based staging model, the final p-tau205-positive stage showed the strongest association with cortical atrophy, cognitive impairment, and risk of progression to dementia (HR = 6.40[4.28-9.59]). These findings support CSF p-tau205 as a biomarker of Alzheimer's disease pathology and progression with potential value for biological staging.
Tau pathology is more closely associated with cognitive deterioration than amyloid burden in symptomatic Alzheimer's disease (AD), yet tau-targeted trials have often interpreted decreases in soluble phosphorylated tau (p-tau) as evidence of therapeutic success. Emerging data argue for a more biology-informed framework. P-tau262 and p-tau356 identify sites within soluble pre-tangle tau assemblies, and cerebrospinal (CSF) p-tau262 may decline as neurofibrillary pathology advances. Conversely, marked p-tau217 lowering with posdinemab was not accompanied by clinical benefit. The amyloid field offers a useful but incomplete analogy. Amyloid plaques are extracellular whereas tau misfolding and fibrillization occur predominantly intracellularly, so equivalent relationships among imaging, fluid biomarkers, and clinical outcomes should not be assumed. A recent preprint describing a functional plasma assay of pathologically active tau reported high discrimination of tau positron emission tomography (PET) positivity, particularly at early tau PET stages, illustrating how seeding-related activity may add information beyond p-tau concentration. We propose a dual-domain framework in which tau-targeted therapies are evaluated using complementary measures of aggregated tau burden and biologically defined soluble tau states. P-tau262 is one candidate within the soluble domain, but treatment-induced increases should be considered favorable only when they accompany aggregate reduction and evidence of a less pathogenic soluble state. This framework applies across antibodies, antisense oligonucleotides, and other biologic tau-directed strategies. Future trials should test joint biomarker-clinical response functions rather than importing thresholds from anti-amyloid therapy, and should prespecify adequately powered analyses of sex, population background, disease stage, and other potential modifiers.
C. Teunissen, L. Pini, B. Imbimbo· Alzheimer's & Dementia· 0 citations
OBJECTIVE
Recent studies suggest that combining plasma phosphorylated tau (p-tau) with β-amyloid (Aβ) may improve diagnosis accuracy for Alzheimer's disease (AD). However, the cross-sectional and longitudinal concordance of these markers with Aβ positron emission tomography (PET) positivity remains incompletely understood. This study aimed to evaluate the diagnostic performance of plasma p-tau, alone and in combination with plasma Aβ, in AD.
METHODS
We included 326 participants from the Alzheimer's Disease Neuroimaging Initiative and 357 Chinese older adults from the Greater-Bay-Area Healthy Aging Brain Study who underwent Aβ-PET imaging. Longitudinal data were available for 285 Alzheimer's Disease Neuroimaging Initiative participants. Plasma p-tau181, p-tau217, Aβ42, and Aβ40 were measured on different analytical platforms. Diagnostic performance for Aβ-PET positivity was assessed using a two-cutoff approach.
RESULTS
Combining plasma p-tau with Aβ42 or the Aβ42/40 ratio reduced the intermediate zone. Notably, p-tau217/Aβ42 showed stronger agreement with Aβ-PET positivity than p-tau217 alone. Among individuals classified as p-tau217/Aβ42 positive but p-tau217 intermediate, 57.1 to 83.3% were Aβ-PET positive. Longitudinally, most Stable Positive (88.0-96.1%) and Stable Negative (89.4-90.9%) cases defined by p-tau217 or p-tau217/Aβ42 were Aβ-PET positive and Aβ-PET negative, respectively. Critically, 69.7 to 75.8% of Non-positive to Positive cases defined by p-tau217/Aβ42 were Aβ-PET positive.
INTERPRETATION
These findings provide novel insights into the cross-sectional and longitudinal diagnostic performance of plasma p-tau217/Aβ42 in AD. To be specific, plasma p-tau217/Aβ42 can reduce the intermediate zone and improve agreement with Aβ-PET positivity, and longitudinal p-tau217/Aβ42 monitoring is particularly informative for identifying Aβ-PET-positive patients who were p-tau217/Aβ42 negative or intermediate at baseline and were misclassified as low risk of AD. ANN NEUROL 2026.
Mingxing Jiang, Guo-Yu Lan, Jiayi Zhu et al.· Annals of Neurology· 0 citations
Plasma biomarkers of amyloid-associated tau phosphorylation (T1) and established tau proteinopathy (T2) can approximate Alzheimer's disease stage, but whether plasma-defined stages correspond to broader biological states is unknown. In 1,035 participants from a multicentre Korean cohort, we used a 220-plex immunoassay platform to compare T1/T2 biomarkers against amyloid and tau positron emission tomography anchors and construct a five-stage framework. Brain-derived phosphorylated tau 217 and endogenously cleaved microtubule-binding-region tau formed the parsimonious backbone. Baseline stage ordered Clinical Dementia Rating-Sum of Boxes trajectories, and forward within-person stage movement was associated with faster clinical worsening. Among 197 non-tau proteins, 34 were stage-associated; the T1-positive transition showed the broadest proteomic shift, with more selective remodelling later. In serial samples, 15 proteins changed longitudinally, with 13 recapitulating the cross-sectional stage pattern. Thus, plasma-defined disease position mapped onto distinct, partly dynamic biological states beyond the defining T1/T2 biomarkers.
Y. Gu, J. Kim, B. Kim et al.· medRxiv· 0 citations
Importance
Phosphorylated tau-217 (p-tau217) is now an established plasma biomarker for assessing amyloid-β pathology in individuals at risk of Alzheimer disease. However, its performance in identifying advanced neocortical neurofibrillary tangle burden remains suboptimal. Precise assessment of tau pathology is increasingly critical for the rational implementation of anti-amyloid therapies and developing anti-tau interventions. Improved biofluid biomarker-based tau staging could enhance patient stratification and optimize participant selection for clinical care and therapeutic trials.
Objective
To develop and validate a multiprotein plasma panel to improve identification of neocortical tau pathology beyond p-tau217 alone.
Design, Setting, and Participants
This multicenter cohort study included 2 independent observational cohorts, Swedish BioFINDER study and Translational Biomarkers in Aging and Dementia (TRIAD). Cross-sectional clinical data and blood samples were collected between 2017 and 2024. Participants included 560 individuals spanning the clinical spectrum from cognitively unimpaired to dementia. These data were analyzed from January 2025 to May 2026.
Exposures
Plasma concentrations of 125 proteins measured using Nucleic Linked Immuno-Sandwich Assay central nervous system panel.
Main Outcome and Measure
Advanced tau pathology defined as tau positron emission tomography (PET) uptake within Braak stage V and VI regions. Predictive performance of biomarker models was evaluated using area under the receiver operating characteristic curve (AUC).
Results
The study included 560 amyloid-positive participants (BioFINDER: n = 431; mean [SD] age, 73.6 [7.0] years; 212 female [49.2%] and 219 male [51.8%]; TRIAD: n = 129; mean [SD] age, 70.4 [8.3] years; 76 female [58.9%] and 53 male [41.1%]). Using multivariable logistic regression approaches, a 7-protein panel was found in BioFINDER to identify tau PET uptake within Braak stage V and VI regions. When compared with p-tau217 (AUC, 0.86-0.88; 95% CI, 0.82-0.94), this multiprotein panel was associated with improved identification in both discovery and validation cohorts (AUC, 0.92-0.94; 95% CI, 0.89-0.98; DeLong P < .001). This reduced the proportion of individuals classified within the intermediate-risk range (between paired sensitivity and specificity thresholds) in the validation cohort by 14.7% to 21.0%.
Conclusions and Relevance
This multicohort study demonstrated how including additional plasma proteins significantly enhanced the performance of p-tau217 in predicting advanced tau pathology among amyloid-positive individuals. This suggests a multiprotein approach may offer a viable and scalable alternative to tau PET staging in clinical or research settings.
Guglielmo di Molfetta, W. Brum, I. Pola et al.· JAMA Neurology· 1 citation
Blood-based biomarkers could broaden access to Alzheimer’s disease diagnostics, but their ability to approximate tau PET, and to address gray-zone results, remains uncertain. We evaluated plasma p-tau217 against tau PET using a harmonized ADNI baseline cohort and an independently derived temporal meta-ROI tau-PET threshold. We included participants with complete baseline plasma biomarkers (p-tau217, Aβ42, Aβ40, NfL, GFAP), tau PET, and demographics, including: cognitively normal = 229, mild cognitive impairment = 149, and Alzheimer’s disease dementia = 41. ROC analyses assessed discrimination of tau-PET positivity overall and by diagnostic group. A two-cutoff strategy was implemented to minimize indeterminate classifications. Across the pooled cohort, p-tau217 demonstrated the strongest ability to discriminate tau-PET status (AUC 0.671, 95% CI 0.597–0.746), outperforming Aβ42, Aβ40, and Aβ42/Aβ40; Though overall accuracy remained moderate and performance differed based on diagnosis, with AUCs of 0.785 for Alzheimer’s disease dementia and lower values for cognitively normal and mild cognitive impairment. The two-cutoff approach substantially reduced intermediate classifications compared with conventional markers. In ADNI, plasma p-tau217 showed the highest discriminative performance among the single blood biomarker for detecting tau-PET positivity, showing moderate accuracy overall and its strongest performance in Alzheimer’s disease dementia. A two-cutoff approach substantially reduces gray-zone classifications, supporting p-tau217 as a primary screening tool before confirmatory imaging. Further work and validation are needed across different groups.
Background The prominent pathological features of Alzheimer's disease (AD) are amyloid-β (Aβ) plaques and tau pathology. The complement cascade is closely related to AD-associated pathological processes; however, the precise mechanisms underlying its contributions remain incompletely elucidated. Objective We aim to investigate the changes in complement protein expression during AD progression. Methods This study enrolled 285 participants from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database. Participants were classified into biomarker-defined groups based on predefined cutoff values for Aβ42 and phosphorylated tau (P-tau). We compared cerebrospinal fluid (CSF) levels of complement proteins (C1q, C2, C3, C4a, C5, C6, C8b, and factor B) across these subgroups. Furthermore, we explored their associations with core AD biomarkers (Aβ42, P-tau, and T-tau) and clinical characteristics. Additionally, we investigated age-related changes in complement gene expression within the cerebral cortex of 3xTg mice using single-nucleus RNA sequencing. Results Complement protein levels in the CSF of A + subjects were significantly lower than those in A− subjects, and complement protein levels were positively correlated with Aβ pathology. Complement protein levels were influenced by factors such as age, gender, body mass index, APOE genotype, and hypertension. Compared with control mice, the complement gene C1qa in microglia was upregulated throughout the entire pathological cycle in 3xTg AD mice. Conclusions Complement proteins undergo significant changes during the pathogenesis of AD, and alterations in their levels may reflect early pathological changes in AD and warrant further investigation. Notably, our findings suggest that microglia may contribute to complement-mediated pathological processes associated with AD.
Ying-Tong Lu, Zi Guo, Meng-Yuan Liu et al.· Journal of Alzheimer's Disea...· 0 citations
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