Evaluation of an Isotope Dilution HPLC Tandem Mass Spectrometry Candidate Reference Measurement Procedure for Total 17-ß Estradiol in Human Serum.

The inaccuracy of 17-ß estradiol (E2) measurements affects its use as a biomarker in patient care and research. Clinical and research communities called for accurate and standardized E2 measurements. Reference Measurement Procedures (RMPs), part of the CDC Hormone Standardization Program (HoSt), are essential in addressing this need and ensuring that methods are accurate and comparable across testing systems, laboratories, and over time. A candidate RMP (cRMP) was developed for the measurement of total E2 in serum using liquid chromatography-tandem mass spectrometry (LC-MS/MS) without derivatization. The cRMP meets suggested performance criteria for accuracy and precision through the use of isotope dilution, calibrator bracketing, and gravimetric measurements. The cRMP demonstrated high agreement with certified reference materials (no significant bias to BCR576, 577, and 578) and established RMPs (slope 1.00, 95% CI 1.00-1.01; intercept 0.02, 95% CI -0.01 to 0.06). The cRMP is highly precise with intra-assay, interassay, and total percent CVs of 2.7%, 1.3%, and 2.4%, respectively. A higher specificity was achieved by measuring E2 without derivatization, compared to methods using derivatization agents. The cRMP can serve as a higher-order standard for establishing measurement traceability and provides an accuracy base against which routine methods can be compared in HoSt.