Elecsys® β-Amyloid (1-42) CSF II

Robust and accurate biomarker tests to aid clinical decisions

Elecsys® β-Amyloid (1-42) CSF II
Robust and accurate biomarker tests to address unmet needs in Alzheimer’s disease

Elecsys® β-Amyloid (1-42) CSF II is an in vitro diagnostic immunoassay intended for the quantitative determination of the β-Amyloid (1-42) (Abeta42) protein concentration. Paired with the Elecsys® Total-Tau (tTau) or Elecsys® Phospho-Tau (181P) CSF assays, the tTau/Abeta42, respectively the pTau181/Abeta42 ratios measure the main 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.1,2

Pathological changes in the β-Amyloid metabolism with accumulation of Abeta42 in plaques are the earliest changes in AD development known so far that can be utilized diagnostically. They are reflected by the decrease in the CSF concentration of Abeta42 as well as by the increase in the brain uptake of the specific tracers on the amyloid PET.1,2,3

Biomarker confirmation of amyloid positivity either by amyloid PET or CSF testing is one of the requirements listed in the appropriate use recommendations for amyloid-targeting therapies.4

The Elecsys® β-Amyloid (1-42) CSF II assay is not intended to be used as a stand-alone test and should only be used with the Elecsys® Phospho-Tau (181P) CSF or Elecsys® Total-Tau (tTau) assays to calculate the ratio of phosphorylated Tau (181P) (pTau181) to β-Amyloid (1-42) (Abeta42) (pTau181/Abeta42 ratio) or Total-Tau (tTau) to β-Amyloid (1-42) (Abeta42) (tTau/Abeta42 ratio).1,2

A negative result, defined as pTau181/Abeta42, respectively tTau/Abeta42 ratio value below their respective cutoffs 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 pTau181/Abeta42, respectively tTau/Abeta42 ratio value above cut‑off, is consistent with a positive amyloid PET scan result.1,2

Although a positive result does not establish a diagnosis of AD or other cognitive disorder, the use of pTau181/Abeta42, respectively tTau/Abeta42 ratio in addition to other clinical diagnostic evaluations enhances diagnosis accuracy and can streamline patient management.1,5,6


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  1. Elecsys beta-amyloid (1-42) CSF II 2022.
  2. Elecsys beta-amyloid (1-42) CSF II 2023.
  3. Lewczuk P, Mroczko B, Fagan A, Kornhuber J. Biomarkers of Alzheimer's disease and mild cognitive impairment: a current perspective. Adv Med Sci. 2015 Mar;60(1):76-82.
  4. Cummings, J., Apostolova, L., Rabinovici, G.D. et al. Lecanemab: Appropriate Use Recommendations. J Prev Alzheimers Dis (2023).
  5. 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.
  6. 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® β-Amyloid (1-42) CSF II

  • Testing time

    18 minutes

  • Test principle

    Two-step sandwich 

  • Calibration


  • Sample material

    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)

    50 pg/mL

  • LoD (Limit of Detection)

    100 pg/mL

  • LoQ (Limit of Quantitation)

    150 pg/mL

  • Measuring range

    150 – 2500 pg/mL

  • Reagent onboard-stability

    16 weeks - cobas e 801 module and cobas e 402 module


    28 days - cobas e 411 analyzer and cobas e 601/602 modules