Endocrine Abstracts

Introduction: Estradiol is an important parameter in the evaluation of female fertility. Moreover, the measurement estradiol is essential in determining the right moment for oocyte retrieval in modified natural cycle IVF (MNC-IVF). Estradiol is measured by an immunochemical method and a change between immunoassays usually comes with a change in reference values due to differences in antibodies used and the lack of harmonization. In our hospital we changed in 2014 from the AutoDELFIA assay (AD) (PerkinELmer) to the Roche method because of continuity. Unfortunately, within a year after the introduction of the Estradiol II assay (E2^II) (Roche) the manufacturer introduced of the Estradiol III assay (E2^III), leading to another change in reference values which is disturbing continuity in patient care.

Methods: Estradiol levels related to follicle size from patients followed in the (MNC-IVF) in 2013 (using AD) were compared with levels from patients from 2015 (using E2^II) by status research. E2^III was compared to E2^II according to the CLSI EP9 and EP5 protocols. Since the given reference levels between the two assays varied more than the two assays differentiated from each other, especially in the ovulatory phase, the E2^III assay was evaluated in 23 patients followed in the MNC-IVF.

Results: The E2^II assay results in ~25% higher estradiol levels compared to AD assay. At follicle size 18 mm average estradiol levels were 0,87 nmol/l (E2^II) vs. 1,06 nmol/l (AD). Passing-Bablok regression from E2^II vs. E2^III was E2^III=0.02+0.93×E2^II over the whole range. In the range used in MNC-IVF patients the comparison was E2^III=0.02+0.85×E2^II.

Conclusion: The E2^III resulted in 15% lower values compared to the E2^II in patients in MNC-IVF, but are more comparable to the formerly used AD. However, the median reference value for the ovulatory phase set by the manufacturer was 44% lower, therefore, new reference values should be set.