Elevate your neurology research journey from discovery to clinical application by consistently detecting phosphorylated-Tau 181 (p-Tau 181) in serum, plasma, or cerebrospinal fluid (CSF).

The Quanterix Simoa® p-Tau 181 assay is a highly sensitive laboratory assay test engineered to quantify p-Tau 181 levels in serum, plasma, or cerebrospinal fluid (CSF) samples. Leveraging Quanterix's Simoa® platform, this pTau-181 assay utilizes digital immunoassay technology that is adept at detecting and measuring biomarkers at ultra low concentrations.

Advantages of utilizing the Simoa® pTau-181 Assay include the following:

  • The ability to monitor disease progression and treatment response over time
  • Compatible with a range of sample types, including blood and CSF, making it a versatile p-Tau 181 assay
  • Highly sensitive and specific detection of p-Tau 181, enabling accurate and early detection of neurodegenerative diseases in research applications

p-Tau 181 in neuropathology

Tau is a microtubule-stabilizing protein that is predominantly found in central nervous system neurons, although it is also slightly expressed in oligodendrocytes and astrocytes. In the human brain, tau is found in six different isoforms, each with a molecular weight ranging from 48,000 to 67,000 daltons. Patients with neurodegenerative diseases and severe head traumas are known to have elevated tau in their CSF, which could indicate that tau is released extracellularly after neuronal damage and serves as a specific biomarker for brain injury.

In Alzheimer’s disease (AD) and related neurodegenerative conditions like chronic traumatic encephalopathy, tau proteins undergo abnormal phosphorylation, leading to the formation of aggregated bundles of filaments. Among the phosphorylation sites on the human tau protein, threonine 181 (p-Tau 181) is particularly notable. Research suggests that p-Tau 181 exhibits a stronger association with AD markers compared to total tau, underscoring its significance in the pathological processes involved in these conditions.

Applications and intended use

The Quanterix Simoa® p-Tau 181 assay is validated for use in discovery and diagnostic research applications. The Simoa® p-Tau 181 assay targets the proline-rich region of the Tau protein, which is highly conserved amongst the tau isoforms. Assays are available for use on the Quanterix HD-X, HD-1, and SR-X instruments, which offer options ranging from benchtop assay prep to automated sample processing and high-throughput capabilities.

● Biomarker discovery and validation: Researchers can use the Simoa® ptau-181 Kit to validate emerging biomarkers, offering researchers a reliable and accurate tool for biomarker discovery workflows.

● Drug discovery: Identify and screen promising drug candidates for further development and testing.

● Research on neurodegenerative diseases: By measuring phosphorylated tau protein levels in the blood, researchers understand the role of ptau-181 in disease process and develop novel diagnostics and neuro-prognostics for such debilitating diseases.

Compatible instruments

  • Advantage Plus: HD-X
  • Advantage: HD-1/HD-X/SR-X

Simoa® pTau-181 V2.1 assay performance


  • Analytical LLOQ: 2.00 pg/mL
  • Functional LLOQ (serum and plasma): 8.00 pg/mL
  • Functional ULOQ (serum and plasma): 1280 pg/mL
  • Functional LLOQ (CSF): 20.0 pg/mL
  • Functional ULOQ (CSF): 12,800 pg/mL
  • LOD: 0.620 pg/mL; range 0.084-1.211 pg/mL
  • Tests per kit: 96


  • Analytical LLOQ: 2.23 pg/mL
  • Functional LLOQ (serum and plasma): 8.92 pg/mL
  • Functional ULOQ (serum and plasma): 1280 pg/mL
  • Functional LLOQ (CSF): 22.3 pg/mL
  • Functional ULOQ (CSF): 12,800 pg/mL
  • LOD: 1.04 pg/mL; range 0.146-1.750 pg/mL
  • Tests per kit: 96

Kit contents

The ready-to-use Simoa® kits include all of the reagents required to perform the p-Tau 181 tests. Each kit has enough reagents for 96 tests.

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