Spuriously elevated serum estradiol concentrations measured by an automated immunoassay rarely cause unnecessary cancellation of in vitro fertilization cycles.

Objective: To report a case of a patient in whom serum E2, as measured by an automated E2 assay, remained elevated at levels corresponding to the periovulatory phase (>380 pg/mL), despite 3 weeks of treatment by a GnRH agonist (GnRH-a).

Design: Case report.

Setting: Tertiary-care academic center.

Patient(s): A 39-year-old patient accepted for IVF treatment. In view of controlled ovarian hyperstimulation, down-regulation by a GnRH-a was monitored by serum E2 measurement.

Intervention(s): Obvious causes for high serum E2 levels (pregnancy, E2-producing ovarian cysts, and noncompliance of the patient) were excluded. The IVF cycle was canceled.

Main Outcome Measure(s): Serum samples were analyzed retrospectively by radioimmunoassay (RIA), and ether extraction of the samples was performed before measurement by the automated E2 assay.

Result(s): Radioimmunoassay revealed adequately suppressed serum E2 levels under GnRH-a treatment (<15 pg/mL). Ether extraction revealed an interfering component that was soluble in the aqueous phase.

Conclusion(s): If a patient on a long controlled ovarian hyperstimulation IVF protocol still has high serum E2 levels after 2 to 3 weeks of down-regulation, and obvious reasons for this (pregnancy, E2 producing ovarian cysts, noncompliance of the patient) are excluded, E2 immunoassay interference should be excluded to avoid unnecessary cancellation of the IVF cycle.