EUROIMMUN microplate ELISA

Principle of the test

  • Polystyrene microplate strips coated with purified, biochemically characterised antigens are used as solid phase containing bound antigens.
  • If the sample is positive, specific antibodies in the diluted serum sample attach to the antigens coupled to the solid phase.
  • In a second step, the attached antibodies are detected with peroxidase-labelled anti-human antibodies.
  • In a third step, the bound antibodies are made visible using a chromogen/substrate solution which is capable of promoting a colour reaction. The intensity of the colour produced is proportional to the concentration of antibodies in the serum sample.
  • The monospecific ELISA (enzyme immunoassays with a single antigen) provides a quantitative in-vitro assay for the detection of antibodies. The "Profile ELISA" provides a semiquantitative in-vitro assay for the detection of different antibodies on a single microplate strip.
  • The solid phase of the "Pool ELISA" is coated with an antigen mixture for the semiquantitative detection of antibodies whose specificity must be investigated subsequently by monospecific assays.

Reliable and economical calibration/evaluation

  • In the case of a quantitative ELISA, calibration is generally performed using three calibration sera.

- Calibration serum 1: upper limit of the measurement range
- Calibration serum 2: upper limit of the normal range (cut-off value)
- Calibration serum 3: negative

  • There is no need for the incubation of blank values or duplicate determinations.
  • Semiquantitative ELISA are performed using only one calibrator. Extended calibration curves are found in some ELISAs for immunity determination or CSF diagnostics.
  • The calibration is performed in relative units (RU/ml) or, if an international reference serum exists, in international units (IU/ml).
  • Each test can be optionally performed using a positive or negative control serum included in the test kit. Kit-specific reference ranges are provided for each calibrator and control serum.
  • All calibration methods can be easily performed with the usual ELISA software.

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Easy, quick and economical handling

  • Microplate strips containing break-off wells (except Profile ELISA).
  • To avoid mix-ups, microplate strips or reagent wells are printed with antigen abbreviations.
  • Reagents ready for use (wash buffer: concentrate).
  • Colour-coding allows clear identification of reagents.

- dark red:   calibration serum 1
- red:   calibration serum 2
- light red:   calibration serum 3
- dark blue:   positive control serum
- green:   negative control serum
- sample buffer and anti-human Ig POD-conjugate: different colours

  • The sample buffer for infectious serology ELISA (detection of antibodies of class IgM) already contains an IgG/RF absorbent.
  • Compatible with all commercial washer and reader systems.

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Determination of low-avidity antibodies

  • An alternative principle for the serological diagnosis of fresh infections has been established by investigating the antibody avidity.
  • The first reaction of the immune system following an infection is the formation of low-avidity antibodies. As the infection proceeds, increasingly antigen-adapted IgG is formed, and avidity grows. As long as high-avidity IgG is not yet detected in the serum, it can be assumed that the infection is still in an early stage.
  • To identify low-avidity antibodies in a patient's serum, two microplate ELISAs are performed in parallel: one test is carried out in the conventional way, the other one includes urea treatment between incubations with patient's serum and peroxidase-labelled anti-human IgG, resulting in the detachment of low-avidity antibodies from the antigens.
  • Low-avidity antibodies are present if the ELISA extinction is significantly reduced by urea treatment. For an objective interpretation, the relative avidity index (RAI) can be calculated out of the measured values with and without urea incubation.
  • Serum dilution 1 : 100, conjugate class anti-human IgG, POD-labelled.
  • 3-point calibration, quantitative (IgG).
  • The following test kits for avidity determination are available: Toxoplasma gondii, CMV, measles virus, rubella virus, VZV, TBE virus, EBV-CA.

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Antibody determination in CSF

  • Indication: local infections of the brain.
  • CSF dilution 1 : 2, serum dilution 1 : 404. Conjugate classes anti-human IgG or IgM, POD-labelled.
  • Easy to conduct: ready-for-use reagents.
  • 4-point calibration, quantitative. Identical incubation conditions and times (room temperature; 60 min / 60 min / 15 min): all EUROIMMUN ELISA for CSF diagnostics can be combined without difficulty on one and the same microplate.
  • The antibody concentration in the patient's serum is determined in parallel to the antibody concentration in CSF on one and the same microplate. The CSF/serum quotient CSQpath.-spec. is calculated from both measured values.
  • An intrathecal synthesis of specific antibodies is present if the CSF/serum quotient of the specific antibodies CSQpath.-spec. is significantly higher than the CSF/serum quotient of the whole IgG (CSQtotal) or if necessary the CSQlim.. The relation of both values indicates the relative CSF/serum quotient CSQrel. (synonym: antibody specificity index, ASI).
  • Interpretation of results (according to the recommendations of Prof. Reiber):
  • CSQrel. < 0.6: unreliable result, check for error
    CSQrel. 0.6 - 1.3: standard range
  • CSQrel. 1.3 - 1.5: borderline range
    CSQrel. > 1.5: Indication of pathogen-specific antibody production in the CNS
  • For the automatic calculation of the CSQrel. EUROIMMUN provides a specific Excel table free of charge.
  • Highest sensitivity, specificity and reproducibility. Antibody concentrations in serum and CSF can be determined over the total linear measurement range.
  • The following test kits for CSF diagnostics are available: Borrelia burgdorferi, Toxoplasma gondii, HSV-1, HSV-2, HSV-1/2 Pool, CMV, rubella virus, measles virus, mumps virus, VZV, TBE, EBV-CA.
  • All test systems for CSF diagnostics can also be used only for serology.
  • Perfectly adapted for the automated incubation in incubation devices.

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