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 gonadotropins and patients treated with oral estrogen.

DESIGN

Prospective study.

SETTING

Assisted Reproductive Technology (ART) program based in a university-affiliated 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): RIA:CIA ratio.

RESULT(S): In the group undergoing gonadotropin stimulation, the median RIA:CIA ratio was 0.92, RIA = 1.26 x CIA(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.