A rapid radioimmunoassay for plasma estrogen

The plasma estradiol equivalent is the total plasma estrogen quantitated by a rapid radioimmunoassay on unextracted plasma. For the radioimmunoassay, 0.1 or 0.2 ml. of plasma is precipitated with methanol, and the supernate is utilized. An internal standard is not required to correct for procedural losses. Dextran-coated characoal solution is used to separate the free and bound steroid. The assay sensitivity is 5 pg. per assay tube (35 pg. per milliliter with a 0.2 ml. plasma sample). The coefficient of variation at this level is 14.3 per cent. The correlation of the plasma estradiol equivalent to the total free plasma estrone, estradiol, and estriol is good (r = 0.962). Thirty plasma samples can be analyzed and reported within 8 hours.