Evaluation and comparison of two fully automated radioassay systems with distinctly different modes of analysis

Two fully automated radioimmunoassay systems with batch and sequential modes of analysis were used to assay serum thyroxine, triiodothyronine, and digoxin. The results obtained were compared with those obtained by manual methods. The batch system uses antibody coated tubes while the sequential system uses immobilized antibody chambers for the separation of bound from free ligands. In accuracy, both systems compared favorable with the established manual methods, but the sequential system showed better precision than the batch system. There was a statistically significant carryover of thyroxine in the sequential system when there were at least six-fold differences in the concentrations of thyroxine in adjacent samples, but the carryover was not significant in the batch system. Compared with the batch system, the sequential system has a shorter throughtime for individual samples (time from aspiration of the sample to the printout of results) but a longer interval for final overall printout of assay results (lower throughput).