Although phosphorylated tau at threonine 231 (pTau 231) is a promising blood-based biomarker for incipient Alzheimer's disease (AD), existing assays such as Simoa® are not sensitive enough to reliably quantify blood pTau 231 in healthy individuals, with reported detectability and quantifiability of 78 % and 40 %, respectively.
This article compares the analytical performance of SPEAR UltraDetect™ pTau 231 Assay and Simoa pTau 231 Advantage PLUS Assay for assessing plasma pTau 231.
The SPEAR assay has higher sensitivity and precision, with 100 % detection and quantification in healthy persons, as well as greater precision (average CV 4.2 % vs. 13.8 % for Simoa).
With enhanced sensitivity and precision, SPEAR UltraDetect enables robust quantification of baseline and subthreshold changes in pTau 231 levels, unlocking the potential of pTau 231 as a plasma biomarker for early AD-detection and longitudinal tracking of disease progression.
Introduction
Early and reliable diagnosis of Alzheimer's pathology is crucial for moving forward with treatment development and improving patient outcomes.
pTau 231 is associated with the earliest cerebral amyloid-beta (Aβ) changes in Alzheimer's disease. Plasma pTau 231 becomes abnormal at preclinical stages with the lowest Aβ burden, compared to other key biomarkers such as pTau217 and pTau181, before the threshold of Aβ-PET positivity is reached.1,2
pTau 231 is a promising biomarker for detecting early Alzheimer's disease and tracking Aβ changes over time in clinical investigations.
pTau 231's promise as a minimally invasive biomarker is restricted. This is because current pTau 231 immunoassays lack the sensitivity and accuracy required to reliably assess baseline pTau 231 levels in blood from healthy and preclinical AD patients, making it difficult to establish pTau 231 as a blood-based AD biomarker.
Successive Proximity Extension Amplification Reaction (SPEAR) is a homogenous, ultrasensitive immunoassay method that addresses the sensitivity limitations and complexity of traditional immunoassays.
SPEAR uses a unique two-factor authentication approach to ensure that amplifiable signals are only created when probes co-localize on target proteins for an extended period of time.
It accurately measures protein biomarkers at attomolar concentrations with as little as 1 µl of diluted sample, outperforming the most sensitive heterogeneous platform on the market.
SPEAR's homogeneous nature eliminates non-specific binding associated with solid surface capture, giving it a higher specificity than heterogeneous immunoassay platforms. SPEAR's procedure eliminates error-prone wash phases, resulting in extremely high precision.
SPEAR UltraDetectTM assays, which are based on this core technology, provide unmatched sensitivity in measuring low-abundance biomarkers while maintaining high specificity and precision. SPEAR UltraDetect reads data using standard qPCR tools, resulting in extremely consistent results across multiple qPCR platforms and formats.
It is simple to integrate into existing laboratory settings and offers exceptional scalability. This article compares the SPEAR UltraDetect pTau 231 Assay to the Simoa pTau 231 Advantage PLUS assay, which has superior sensitivity and precision in plasma samples.
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About Spear Bio
Spear Bio is an innovative leader in providing scalable solutions for ultra-sensitive protein biomarker measurements. Spear Bio’s proprietary technology, Successive Proximity Extension Amplification Reaction (SPEAR), employs a unique 2-factor authentication mechanism to precisely measure protein biomarkers at attomolar level from sub-microliter sample volume. Spear Bio is focused on leveraging its technology’s unprecedented sensitivity to transform protein research and early disease diagnosis.
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