The DiaSource CEA-IRMA is an immunoradiometric assay based on coated-tube separation.
Mabs1, the capture antibodies, are attached to the lower and inner surface of the plastic tube. Calibrators or samples added to the tubes will at first show low affinity for Mabs1. Addition of Mab2, the signal antibody labelled with 125I, will complete the system and trigger the immunological reaction.
After washing, the remaining radioactivity bound to the tube reflects the antigen concentration. The use of several distinct Mabs avoids hyperspecificity, common to two-site IRMA, as well as a need of a shaker or long incubation at 37°C.