Rubella Ab IgG fast is an one-step sandwich assay based on microwells coated with recombinant antigens of Rubella virus (rAg). The conjugate is a mixture of HRP-labeled polyclonal goat anti-human-IgG antibodies. Serum samples are added to the wells and if anti-Rubella virus antibodies are present in a sample, they form stable complexes with antigens immobilized on the wells. Then the antigen-antibody complexes are identified by the addition of HRP labeled anti-human-IgG conjugate. The unbound components are removed by washing. After addition of the solution containing TMB and hydrogen peroxide, the wells with bound conjugate develop a blue colour which is converted to yellow after the reaction has been stopped with sulphuric acid. The colour intensity is directly proportional to the concentration of IgG antibodies to Rubella virus in the specimen and can be read at 450 nm.