For in vitro diagnostic use. The RIDA®Aviditätsreagenz is an additional reagent to the RIDA®LINE Parvovirus B19 IgG blot for determination of IgG avidity.
The classical serology of infectious diseases is based on the observation that IgM-antibodies specific to a certain type of pathogen are formed only temporarily, whereas the respective IgG response continues for a long time. For this reason, IgM diagnosis indicates acute infection, but IgG diagnosis without parallel IgM is a sign of past infection. Due to the variability of immune response and to the occur-rence of aberrant serological processes (e.g. persistent, reactivated or absent IgM response) this classical approach may lead to false conclusions in many cases. Avidity describes the binding strength of specific antibody to antigen. It was found to be low in the first phase after primary infection but then to increase over time.
In addition to classic serodiagnosis, measurement of avidity provides information making it possible to distinguish between acute and past infection. During IgG response there is a continuous increase in the avidity of IgG for the respective an-tigen. This occurs as an immunological principle. For this reason, IgG with a low avidity is usually present in acute infection and IgG with high avidity is present after infection has ended. As a result of this observation, another very significant marker has been introduced into diagnosis in the last few years: the avidity of IgG.
Two test strips are incubated with the diluted serum sample for each test run. During this initial incubation, antibodies in the sample bind to their specific antigens, which are fixed on the test strips. Then one of the two test strips is washed with avidity solution. During this step, the low avid antibodies are removed by diffusion while the high avid antibodies remain bound to their specific antibodies. Following the washing step, anti-human antibodies conjugated with horse radish peroxidase are added. The specific antibodies bound to their antigens is made visible by adding a substrate that forms bands on the test strips. The relative position of the coloured bands indicates the specificity of the reacting antibodies. Subsequent comparison of the two test strips then provides a basis for measuring the avidity of the antibodies and for establishing the stage of infection.
|Test format||Avidity reagent (lyophyllisate) for 25 determinations|