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 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 is 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.

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.

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.