Serum levels of estradiol (E2) may be monitored in a postmenopausal woman with breast cancer to make sure that estradiol production is suppressed. Falsely elevated values can occur if an immunoassay is used to measure estradiol.
Medications reported to cause falsely elevated values by immunoassay:
(1) fulvestrant (Faslodex)
(2) exemestane (Aromasin)
Other causes:
(1) human anti-animal antibodies (if monoclonal antibody used as a reagent)
(2) elevated serum CRP or CRP-associated factor (Ohlsson et al)
Differential diagnosis of changes in serum estradiol concentrations:
(1) fluctuations in the perimenopausal state
(2) use of different immunoassays to measure the estradiol over time
For patients with breast cancer, liquid chromatography/mass spectroscopy is recommended for monitoring rather than immunoassay.
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