Rapid, convenient radioimmunoassay of estrone sulfate

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Abstract
We developed a specific, simple, and rapid RIA for the direct quantification of estrone sulfate (E1S) and established its performance characteristics. The assay has a dynamic range of 0.05–90 μg/L with a detection limit of 0.009 μg/L. Intraassay CVs were 9.2%, 4.5%, and 4.6% at 0.35, 9.0, and 60 μg/L, respectively. Interassay CVs were 8.8%, 5.1%, and 5.5% at 0.076, 0.5, and 12 μg/L, respectively. Linearity of dilution studies showed values of 80–105% of expected, and recovery of E1S added to serum samples ranged from 82% to 102%. Cross-reactivities with structurally related estrogens were 1S and indirect measurement of estrone), the present RIA showed excellent correlation (r = 0.99, slope = 1.54, Sy‖x = 2.14, n = 71). Mean E1S concentrations measured with this RIA for normal men (n = 20) and women in follicular (n = 20) and luteal (n = 25) phases of their menstrual cycle were 0.96, 0.96, and 1.74 μg/L, respectively. Mean E1S concentrations for oral contraceptive users (n = 20) and postmenopausal women without hormone replacement therapy (n = 21) or on hormone replacement therapy (n = 22) were 0.74, 0.13, and 2.56 μg/L, respectively. Serum concentrations of E1S in pregnant women in their first (n = 14), second (n = 17), and third (n = 15) trimesters were 20, 66, and 105 μg/L, respectively. Availability of this simple RIA should provide a useful tool for the assessment of estrogen status in women.