Evaluation of a Radioimmunoassay for Estradiol in Unextracted Serum

We describe the performance of a commercial (Steranti/EIR) RIA reagent kit for measuring 17p-estradiol directly in serum. Day-to-day precision data for control sera were as follows: mean = 102.8 ng/L, CV = 6.8%, n = 20; mean = 231.1 ng/L, CV = 5.3%,n = 21; mean = 747.7 ng/L, CV = 9.4%, n = 21. Analytical recovery of added estradiol from seven different serum pools from men, to which three different concentra-tions of estradiol had been added, was (mean ± SD): 98.6 ± 7.0 % at 107.5 ng/L added; 98.8 ± 4.7 % at 322.5 ng/L added; 108.2 ± 4.8 % at 645 ng/L added. Overall recovery of estradiol in these experiments (mean ± SD for 21 determina-tiOns) averaged 101.9 ± 7.0%. Assay of 32 serum speci-mens from women by both the direct (y) and an extraction method (x) gave the following linear regression statistics: y = 1.12x- 1.3, r = 0.998, = 30.2 ng/L, meany = 438.2ng