Rapid, convenient radioimmunoassay of estrone sulfate

¹ Diagnostic Systems Laboratories, 445 Medical Center Blvd., Webster, TX 77598-4217.

² Diagnostic Systems Laboratories, 600 University Ave., Room 653, Toronto, Ontario M5G1X5, Canada.

³ Texas Tech University, Health Science Center, Department of Obstetrics and Gynecology, 1400 Wallace Rd., Amarillo, TX 79106-1797.

⁴ University of Southern California School of Medicine, Women and Children's Hospital, 1240 N. Mission Rd., Los Angeles, CA 90033.
^a Author for correspondence. Fax (281) 554-4220.

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 <5%. When compared with a conventional assay (involving hydrolysis of E₁S and indirect measurement of estrone), the present RIA showed excellent correlation (r = 0.99, slope = 1.54, S_yx = 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.

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