A rapid radioimmunoassay for serum unconjugated estriol with a directly iodinated estriol radioligand.

Radioiodinated estriol not previously derivatized was found to be immunoreractive and is shown to possess Sephadex-adsorptive characteristics similar to those of tritium-labeled estriol and nonlabeled estriol. Because of these characteristics, radioiodinated estriol is shown to be an acceptable radioligand for use in a rapid and reliable column radioimmunoassay for determination of unconjugated estriol in serum. An evaluation of the estriol column RIA assay with this radioligand is presented.