pTau231 Biomarker Assay Kit for Alzheimer’s Research

A blood biomarker of early-stage amyloid pathology

pTau231 (phosphorylated tau at threonine 231) is a blood-based biomarker that reflects early tau phosphorylation changes associated with amyloid-β pathology. It correlates with brain amyloid status as measured by PET and CSF. pTau 231 is one of the earliest tau epitopes to phosphorylate in Alzheimer’s disease suggesting strong potential for detecting preclinical Alzheimer’s disease. pTau 231 is used in research for early disease detection, risk stratification, and to study the temporal sequence of amyloid and tau pathology.

Unparalleled Sensitivity with SPEAR UltraDetect pTau 231

The SPEAR UltraDetect pTau 231 assay demonstrates unparalleled sensitivity, delivering high quantifiability – important for exploration of pTau 231 as an early marker in longitudinal studies and potential applications in clinical trials.

In a study comparing a cohort of PET-confirmed amyloid positive and amyloid negative patient samples, SPEAR UltraDetect quantified 100% of samples – including amyloid negative samples with average CV of 5%.

SPEAR UltraDetect pTau 231 quantifies 100% of AD and non-AD patient plasma samples
[1 µL diluted sample]

EDTA Plasma samples (n=40) of AD and non-AD patient samples measured on SPEAR UltraDetect pTau 231

Assay Specifications

MRD	4X
Diluted Sample Volume	1µL
Raw Sample Volume to Machine	10 µL
LOD (pg/mL)	0.039
fLLOQ (pg/mL)	0.330
Spike-recovery (% recovery)	103%
Linearity (% recovery)	89%
Intra-plate CV (AVG %)	2.82%
Inter-plate CV (AVG %)	6.47%
EDTA Plasma Quantifiability	97%

Supporting Alzheimer’s Disease Research at Any Scale

pTau231 is a highly informative biomarker that reflects early tau phosphorylation changes associated with amyloid accumulation and paired helical filament formation. Levels of pTau231 are often elevated in Alzheimer’s disease (AD) and have been studied alongside markers like pTau217 and neurofilament light to monitor central nervous system pathology.

While traditional methods for detecting phosphorylated tau offer valuable insights, such as conventional and digital ELISA kits or cerebrospinal fluid (CSF) analysis, they often involve invasive collection, workflow complexity, and lack of reliable sensitivity.

The SPEAR UltraDetect™ pTau231 assay provides a blood-based alternative offering unmatched analytical performance without the limitations of traditional immunoassays. Researchers can rely on this assay to support:

Multi-marker strategies (e.g., with pTau271 or neurofilament light)
Monitoring biomarker changes in at-risk or early-stage AD cohorts
Therapeutic trial enrichment based on biomarker classification
Translational research connecting blood-based and CSF biomarker trends

Recommended for Research Across Sample Types and Settings

The SPEAR UltraDetect™ pTau231 assay is intended for Research Use Only (RUO) and is optimized for use with plasma. Its sensitivity, specificity, and precision make it particularly well-suited for studies in therapeutic development pipelines, and early-intervention research programs.

By enabling highly-accurate, low-volume detection of pTau231, this assay supports investigations into neurodegenerative disease mechanisms and strengthens biomarker-driven decision-making in Alzheimer’s research.

Designed for Sensitivity and Specificity Without Compromise

Compared to traditional methods reliant on CSF samples or surface-based formats, SPEAR’s wash-free, homogeneous approach reduces variability and complexity—while maintaining unparalleled sensitivity at the attomolar level.

SPEAR’s two-factor authentication system confirms each detection event through two independent molecular interactions, reducing false positives and delivering the high specificity needed to confidently interpret low-abundance signals.