Is chemiluminescent immunoassay an appropriate substitution for radioimmunoassay in monitoring estradiol levels?

Objective: To determine the correlation between serum estradiol measurements by chemiluminescent immunoassay (CIA) vs. radioimmunoassay (RIA) in two groups: patients treated with gonadstropins and patients treated with oral estrogen. Design: Prospective study. Setting: Assisted Reproductive Technology (ART) program based in a university-affiliate hospital in Manhasset, New York. Patient(s): Three hundred forty-eight patients undergoing gonadotropin stimulation and 63 patients receiving oral estrogen between July and December, 1997. Intervention(s): Estradiol levels were measured concomitantly on all patients undergoing gonadotropin stimulation for IVF and all patients receiving oral estrogen for a frozen-thaw cycle. Main Outcome Measure(s): RTA:CIA ratio. Result(s): In the group undergoing gonadotropin stimulation, the median RIA:CIA ratio was 0.92, RTA = 1.26 X CLA(0.96), r = 0.98. In the group receiving oral estrogen, the median ratio was 3.93, RIA = 2.9 X CIA(1.05), r = 0.89. Conclusion(s): Estradiol levels determined by CIA correlate closely with RIA results for patients being treated with gonadotropins. Conversely, for patients receiving oral estrogen, CIA levels are one-third or less of the RIA level. (C) 2000 by American Society for Reproductive Medicine.