Relative potencies of four CEA preparations assayed by three commercial radioimmunoassay kits

An attempt has been made to determine relative potencies of four Carcinoembryonic Antigen (CEA) reference preparations, including the World Health Organization CEA standard, assayed by three kits (Abbott, Cis, Roche). For some kits and reference CEAs, relative potencies varied as a function of the concentration at which CEAs were assayed; whether this was due to different CEA antigenicities or to inappropriate technical conditions (e.g. unequal adsorption of CEA onto surfaces, in connection either to the protein composition of buffers or to different degrees of purification of CEAs) requires further investigation. Even when the CEA concentration had no influence, relative potencies differed according to the origin of the kits. Since even when a single reference material is used, different relative potencies are obtained with different kits, valid comparisons can hardly be made, at least for the time being, unless the same technique and the same test system (antiserum and antigen) are used. Modalities of such a technique should be carefully determined and the reagents carefully selected so that lack of parallelism, if any, between CEA of different origins can only be ascribed to differences in antigenicity.