pTau 217: A Blood Biomarker for Alzheimer’s Disease Pathology
pTau 217 (phosphorylated tau at threonine 217) is a highly specific blood-based biomarker of brain amyloid β pathology. Validated against PET imaging and CSF Aβ42/40, it has demonstrated high sensitivity and specificity for identifying amyloid positivity, often outperforming other plasma markers such as pTau181 or Aβ42/40. These properties make pTau 217 a valuable tool for early detection, noninvasive screening, and disease tracking in diagnostic research, therapeutic trials, and longitudinal studies for AD.
While most pTau 217 assays measure a broader population of circulating pTau 217 species, the SPEAR TrueDetect™ epTau 217 Assay measures a distinct subset defined by phosphorylation at threonine 217 and the absence of phosphorylation at serine 199.
Highly Specific Plasma pTau 217 Measurement with SPEAR epTau 217
The SPEAR epTau 217 assay has demonstrated unparalleled specificity in differentiating Alzheimer’s disease and non-AD patient samples. Combined with its sensitivity and precision (quantifying 100% of healthy samples above fLLOQ), SPEAR epTau 217 offers researchers a powerful tool to better characterize blood based samples in Alzheimer’s research.
In a study to demonstrate SPEAR epTau 217 performance, CSF- and PET-confirmed Alzheimer’s Disease (AD) and non-AD samples were both tested. In this combined cohort study, SPEAR TrueDetect epTau 217 demonstrated a 5.41x mean fold-difference between groups and area under the curve (AUC) of 0.989 for CSF-confirmed samples and 0.984 for PET-confirmed samples. This level of differentiation and predictive power highlights the SPEAR epTau 217 assay in its ability to classify Alzheimer’s and non-Alzheimer’s patient plasma samples.
SPEAR epTau 217 fold-difference in AD and Control samples
[1 µL diluted sample]
SPEAR epTau 217 testing on CSF-confirmed EDTA Plasma AD and non-AD (Control) including 48 non-AD and 40 AD. Amyloid PET confirmed EDTA plasma including 33 Amyloid negative (Control) and 28 Amyloid positive (AD)
SPEAR epTau 217 ROC for CSF-confirmed and PET-confirmed plasma samples
[1 µL diluted sample]
SPEAR epTau217 ROC analyses on CSF-confirmed EDTA Plasma AD and non-AD (Control) including 48 non-AD and 40 AD. Amyloid PET confirmed EDTA plasma including 33 Amyloid negative (Control) and 28 Amyloid positive (AD)
Assay Specifications
| MRD | 4X |
| Diluted Sample Volume | 1µL |
| Raw Sample Volume to Machine | 10µL |
| LOD (pg/mL) | 0.005 |
| fLLOQ (pg/mL) | 0.080 |
| Spike-recovery (% recovery) | 106% |
| Linearity (% recovery) | 87% |
| Intra-plate CV (AVG%) | 3.32% |
| Inter-plate CV (AVG%) | 4.43% |
| EDTA Plasma Quantifiability | 100% |
The SPEAR pTau 217 blood test was awarded FDA Breakthrough Device Designation in January 2025, recognizing its potential to transform Alzheimer’s disease (AD) diagnosis. This innovative blood test for pTau 217 offers a less invasive and more accessible alternative to traditional methods like Mass Spectrometry, PET scans and CSF analysis. Designed to detect plasma pTau 217—a core biomarker for Alzheimer’s—the test delivers the sensitivity and specificity needed to accurately measure low concentrations in blood. By supporting research into earlier and more reliable diagnosis, the pTau217 biomarker assay shows strong potential to help distinguish Alzheimer’s from other neurological conditions and expand patient access to timely interventions and emerging therapies.
Supporting Alzheimer’s Disease Research at Any Scale
Whether you’re investigating biomarker dynamics in mild cognitive impairment (MCI) patients or tracking treatment response in longitudinal studies, the SPEAR epTau217 blood test offers robust, reproducible data that aligns with established CSF biomarkers and amyloid PET imaging. By minimizing invasiveness and complexity, the assay is ideal for:
- Multi-marker strategies (e.g., with pTau231 or neurofilament light)
- Clinical trial endpoints and cohort enrichment
- Preclinical screening of candidate therapeutics
- Integration with exploratory pipelines
Recommended for Research Across Sample Types and Research Settings
The SPEAR epTau217 assay is intended for Research Use Only (RUO) and is designed for use with plasma samples. Its unparalleled specificity makes it well-suited for a wide range of research applications, including those involving memory clinic cohorts and therapeutic development studies. The assay’s exceptional analytical performance supports investigation of biomarker trajectories, Aβ positivity, and cognitive decline—offering a scalable alternative to Mass Spectrometry, ELISA- or PET-based methods in Alzheimer’s disease research.
Designed for Sensitivity and Specificity Without Compromise
Researchers seeking performance without operational complexity will appreciate the SPEAR platform’s elegant assay design. SPEAR’s two-factor authentication mechanism and homogeneous format ensure that each pTau217 molecule in a sample is independently verified twice, eliminating false positives and ensuring highly-specific measurement of plasma pTau217 levels, even in challenging blood matrices.
The assay works with samples of 1 µL of diluted sample, enabling repeated analysis from scarce or precious specimens—such as those collected in longitudinal neurodegeneration studies.
From Evaluation to Disease-Modifying Therapy Development
Whether you’re researching biomarkers for Alzheimer’s disease, exploring tau protein kinetics, or validating candidate disease-modifying therapies, the robust SPEAR TrueDetect™ epTau 217 assay kit empowers you to move forward with confidence that comes from results with unparalleled sensitivity, specificity, and precision. The assay’s simplicity makes it a practical tool for research labs of all sizes, aiding the advancement of research from the bench to the clinic.
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