This test kit is an immunoradiometric assay (IRMA) based on coated-tubes with monoclonal antibodies directed against distinct epitopes of the molecule of TG.
Three capture antibodies are coated on the inner wall of tubes. TG of the calibrators or of the samples is captured by these antibodies. Addition of the fourth antibody labeled with 125Iodine completes the system, allowing the formation of a bridge between the coated antibodies and the labeled antibody.
After washing, the remaining radioactivity bound to the tubes is directly related to the concentration of TG in the calibrators or samples. The careful choice of the four monoclonal antibodies allows high specificity and high sensitivity and avoids excess of specificity which is sometimes reproached to immunometric assays with only two monoclonals.