VarelisA Test Principle

The VarelisA test is an enzyme linked immuno sorbent assay (ELISA) and is designed as a sandwich immunoassay.

A well is coated with the antigen recognized by the target antibody which is specific for a particular autoimmune disease. If this specific antibody is present in the patient’s blood sample, it will bind to the antigen. In the subsequent reaction step, an enzyme-conjugated secondary antibody binds to the target antibody. Because of the enzyme, the substrate is transformed into a colored substance. By comparing the color intensity generated by the test sample with that of standards of known concentrations, the antibody concentration in the test sample can be determined.

The antigen of interest, coated to the solid phase, binds the specific  antibodies (e.g. of IgG class) in the patient sample.
After washing away unbound, non-specific antibodies, enzyme labelled antibodies against the target antibody (e.g. of IgG class) are added to form a complex.
After incubation, unbound enzyme labelled antibodies are washed away and the bound complex is then incubated with an enzyme substrate.
Because of the enzyme, the substrate is transformed into a coloured product. After stopping this reaction, the colour intensity of the sample is measured. The higher the colour intensity is, the more specific antibodies (e.g. of IgG class) are present in the sample.