Elecsys® Total -Tau CSF

Robust and accurate biomarker tests to aid clinical decisions

Elecsys® Total -Tau CSF
Robust and accurate biomarker tests to address unmet needs in Alzheimer’s disease

Elecsys® Total-Tau CSF (tTau) is an in vitro diagnostic immunoassay intended for the quantitative determination of the total tau (the 6 human brain Tau isoforms) protein concentration in human cerebrospinal fluid (CSF). Paired with the Elecsys® β-Amyloid (1-42) CSF assay, the tTau/Abeta42 ratio measures two biomarkers of Alzheimer’s pathology, beta-amyloid 42 and tau proteins, in adults ages 55 and older being evaluated for AD or other causes of cognitive impairment.1

Studies have shown that while CSF β‑Amyloid (1‑42) levels decrease to around half the level in controls, CSF tTau levels increase around 2‑3 fold in mild-moderate AD patients compared to age‑matched controls.2,3

The Elecsys® Total-Tau CSF assay is not intended to be used as a stand-alone test and should only be used with the Elecsys® β-Amyloid (1-42) CSF assay to calculate the ratio of Total-Tau (tTau) to β-Amyloid (1-42) (Abeta42) in CSF (tTau/Abeta42 ratio).1

A negative result, defined as tTau/Abeta42 ratio value below cutoff is consistent with a negative amyloid positron emission tomography (PET) scan result and reduces the likelihood that a patient’s cognitive impairment is due to AD. A positive result, defined as tTau/Abeta42 ratio value above cut off, is consistent with a positive amyloid PET scan result.1

Although a positive result does not establish a diagnosis of AD or other cognitive disorders, the use of tTau/Abeta42 ratio in addition to other clinical diagnostic evaluations enhances diagnosis accuracy and can streamline patient management.1,4,5


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  1. Total-Tau (tTau) CSF method sheet 2023-04.
  2. Mattsson N, Zetterberg H, Hansson O, et al. CSF biomarkers and incipient Alzheimer disease in patients with mild cognitive impairment. JAMA. 2009;302(4):385-393. 
  3. Hampel H, Blennow K. CSF tau and β-amyloid as biomarkers for mild cognitive impairment. Dialogues Clin Neurosci. 2004;6(4):379-90.
  4. Sabbagh MN, Lue LF, Fayard D, Shi J. Increasing Precision of Clinical Diagnosis of Alzheimer's Disease Using a Combined Algorithm Incorporating Clinical and Novel Biomarker Data. Neurol Ther. 2017;6(Suppl 1):83-95.
  5. Hansson, O. et al. (2018). CSF biomarkers of Alzheimer’s disease concord with amyloid-β PET and predict clinical progression: A study of fully automated immunoassays in BioFINDER and ADNI cohorts. Alzheimers Dement 14(11), 1470-1481.

Elecsys® Total -Tau CSF

  • Systems

    cobas e 411 analyzer, cobas e 601 / cobas e 602 modules, MODULAR ANALYTICS E170

  • Testing Time

    18 minutes

  • Test principle

    Sandwich principle

  • Calibration


  • Traceability

    LC-MS/MSTau (172-205) [pThr181]amidTau (156-166) – Tau (192-202) – Tau (217-227) amid

  • Sample material

    Human Cerebrospinal Fluid (CSF)

  • Sample volume

    30 µL - cobas e 801 module and cobas e 402 module 

    50 µL - cobas e 411 analyzer and cobas e 601/602 modules








  • LoB (Limit of Blank)

    30 pg/mL

  • LoD (Limit of Detection)

    60 pg/mL

  • LoQ (Limit of Quantitation)

    80 pg/mL

  • Measuring range

    8-1,300 pg/mL (defined by the Limit of Quantitation and the maximum of the master curve)

    Values below the Limit of Quantitation are reported as < 80 pg/mL

    Values above the measuring range are reported as > 1,300 pg/mL

  • Intermediate precision

    cobas e 411: 2.2-3.5% (4.14 - 40.3 pg/mL)
    E170, cobas e 601, cobas e 602: 1.4% -2.1% (1.63 – 19.5 pg/mL)