57Co: a volume marker for the triple-isotope, double-antibody radioimmune assay

A prototype triple-isotope, double-antibody radioimmune assay for the analysis of large numbers of samples on a routine basis has previously been reported (Egan, M.L. Lautenschleger, J.T., Coligan, J.E., and Todd, C.W., 1972, Immunochemistry, vol.9,289). The major advantage of this technique is that almost instantaneous computer calculations replace the tedious and often error-prone step of washing the precipitate as the last step in the assay procedure. The 22Na used as a volume marker in the original procedure can be replaced by 57Co provided a chelating agent is present to prevent its adsorption to serum proteins. Because of its decay pattern, 57Co can be counted with greater efficiency with less overlap into other channels. Other features which recommend its use are the lower cost and its lower gamma radiation level which results in reduced exposure of personnel to radioactivity. (author)