A rapid 5 hour radioimmunoassay of progesterone and oestradiol in human plasma.

A rapid 5 h radioimmunoassay method for the determination of progesterone and oestradiol in the plasma of non-pregnant women is described. Due to the high specificity of the antisera used, it is possible to perform the radioimmunoassay directly on the ether extracts of plasma, without employing chromatographic purification of the steroids. Evidence is presented indicating that the rapid assay is almost as reliable as the previously described radioimmunoassay method which involves chromatography. The within-assay and between-assay coefficients of variation in the progesterone assay were 7-74 and 14-9 and in the oestradiol assay 7-36 and 18-1 respectively. Comparisons between increasing doses of authentic hormone and endogenous hormone extracted from plasma indicated no deviation from parallelism. Progesterone and oestradiol were assayed in 300 plasma samples by the rapid method and by the method involving chromatography. The slopes obtained by a regression analysis were close to unity for both progesterone and oestradiol (1-04 and 1-06, respectively), the y-intercepts were - 0-21 and 0-16 and the correlation coefficients 0-98 and 0-88, respectively. When the data obtained by both techniques in fourteen menstrual cycles were compared, the results were practically identical. In ten repeated studies conducted by four investigators it was shown that two workers can complete the assay of both progesterone and oestradiol in twenty-five plasma samples in duplicates with 5 h. The same time required for the assay of either progesterone or oestradiol in twenty-five duplicates by one worker.