Comparison of enzyme immunoassay with dextran-coated charcoal method in the determination of progesterone receptor in breast cancer cytosols.

A new enzyme immunoassay (EIA) for progesterone receptor (PR) has been developed by Abbott Laboratories. To study the correlation of the results from this new technique with the currently existing tritiated-ligand binding assay [dextran-coated charcoal (DCC) method], cytosols from 70 human breast cancers were assayed for PR by both the EIA and DCC methods. EIA showed a good reproducibility and was not susceptible to the change in protein concentration of cytosols and types of reducing agents. The correlation between the EIA and DCC methods was excellent with a correlation coefficient of 0.946; regression curve was PR (EIA) = 1.06 X PR(DCC) + 0.19 fmol/mg protein. The concordance of the results obtained from both methods was 91.4% with a cutoff value of 10 fmol/mg protein. These results demonstrate that EIA is a very useful and reliable method in the determination of PR with an excellent correlation with the conventional DCC method.