Estimation of true values in radioimmunoassays.

We tested the accuracy of radioimmunoassays for two hormones, progesterone and estradiol, in relation to the use of two different antisera in each assay and to the degree of purification from plasma before the assay was done. Each analyte was assayed either in a diethyl ether extract, in a zone eluted from a Sephadex LH-20 chromatographic column, or in fractions of a chromatographic zone (from Sephadex LH-20 or Celite) that passed a test of "radiochemical purity." Statistically indistinguishable results were obtained in the assay of radiochemically pure fractions of both analytes, irrespective of the antiserum used.