RAPID, CONVENIENT RADIOIMMUNOASSAY OF ESTRONE SULFATE

We developed a specific, simple, and rapid RIA for the direct quantifi cation of estrone sulfate (E1S) and established its performance charac teristics. The assay has a dynamic range of 0.05-90 mu g/L with a dete ction limit of 0.009 mu g/L. Intraassay CVs were 9.2%, 4.5%, and 4.6% at 0.35, 9.0, and 60 mu g/L, respectively. Interassay CVs were 8.8%, 5 .1%, and 5.5% at 0.076, 0.5, and 12 mu g/L, respectively. Linearity of dilution studies showed values of 80-105% of expected, and recovery o f E1S added to serum samples ranged from 82% to 102%. Cross-reactiviti es with structurally related estrogens were <5%. When compared with a conventional assay (involving hydrolysis of E1S and indirect measureme nt of estrone), the present RIA showed excellent correlation (r = 0.99 , slope = 1.54, S-y\x = 2.14, n = 71). Mean E1S concentrations measure d with this RIA for normal men (n = 20) and women in follicular (n = 2 0) and luteal (n = 25) phases of their menstrual cycle were 0.96, 0.96 , and 1.74 mu g/L, respectively. Mean E1S concentrations for oral cont raceptive users (n = 20) and postmenopausal women without hormone repl acement therapy (n = 21) or on hormone replacement therapy (n = 22) we re 0.74, 0.13, and 2.56 mu g/L, respectively. Serum concentrations of E1S in pregnant women in their first (n = 14), second (n = 17), and th ird (n = 15) trimesters were 20, 66, and 105 mu g/L, respectively. Ava ilability of this simple RIA should provide a useful tool for the asse ssment of estrogen status in women.