Solid-phase chemiluminescence immunoassay for plasma estradiol-17 beta during gonadotropin therapy compared with two radioimmunoassays.

Estradiol in plasma was determined with a simple solid-phase immunoassay based on chemiluminescence in patients undergoing ovulation induction. In the assay, we use a purified monoclonal antibody to estradiol-17 beta, with estradiol-6-carboxymethyl oxime-aminobutylethyl isoluminol as the chemiluminescent marker. The antibody is covalently coupled to polymer beads. Bound and free ligand are separated by simple centrifugation. Values so determined were compared with those determined with two different radioimmunoassay (RIA) methods, one involving the same monoclonal solid-phase antibody plus iodinated estradiol, 125I-RIA, the other a polyclonal antibody and tritiated estradiol, 3H-RIA. In the latter RIA, dextran-coated charcoal was used to separate bound and free ligand. Values determined by the three methods agreed well: for chemiluminescence vs 125I-RIA, r = 0.93; for chemiluminescence vs 3H-RIA, r = 0.94; for 125I-RIA vs 3H-RIA, r = 0.94. The three methods are similar in sensitivity, specificity, and precision. The present method is simple and reliable, taking advantage of the specificity and sensitivity intrinsic to the use of an antibody without the inconveniences associated with use of an isotopically labeled ligand.