Adaptation of a T3-uptake test and of radioimmunoassays for serum digoxin, thyroxine, and triiodothyronine to an automated radioimmunoassay system--"Centria"

Abstract

We report the adaptation of four radioassays to the prototype of an automated radioimmunoassay system ("Centria," Union Carbide). The system consists of three integrated modules: (a) an automated pipettor, which dispenses samples and reagents; (b) the key module, an incubator/separator, in which centrifugal force is used to initiate and terminate multiple radioassay incubations and separations simultaneously; and (c) a gamma-counter/computer, which counts three tubes simultaneously and converts counts into concentration units. Radioimmunoassays for thyroxine, triiodothyronine, and digoxin were developed with use of well-characterized antibodies and of prepackaged Sephadex-containing columns to separate bound and free radioactive ligand. A triiodothyronine-uptake test in which the same kind of columns were used was also adapted to the instrument. Results for clinical samples compared favorably with those obtained by manual procedures. We report data on correlation between different methods and preliminary data on precision of the prototype system.