Development and validation of a LC-MS/MS assay for quantification of serum estradiol using calibrators with values assigned by the CDC reference measurement procedure.

BACKGROUND: Estradiol was historically measured by gas chromatography-mass spectrometry before development of immunoassays. Although immunoassays were fast requiring low sample volume, they had specificity issues. More recently, liquid chromatography-tandem mass spectrometry became the methodology of choice for estradiol quantitation in serum. However, one thing all methods have in common is lack of standardization.

METHODS: A LC-MS/MS assay was developed and clinically validated using calibrators with concentrations assigned by a Reference Measurement Procedure in an effort to increase accuracy of calibration.

RESULTS: Two hundred microliters of serum was subjected to liquid-liquid extraction using hexane:ethyl acetate followed by derivatization using dansyl chloride. Gradient elution had a run time of 6.5 min. The analytical measurement range was 2 to 1000 pg/mL with between-run imprecision of <10%. Method comparisons with two reference laboratories showed acceptable bias and so did Reference Materials from the European Commission Joint Research Center, Institute for Reference Materials and Measurements and the College of American Pathologist Accuracy-Based survey samples.

CONCLUSIONS: A LC-MS/MS assay for serum estradiol was developed and clinically validated with calibrator concentrations assigned by the CDC RMP to help improve accuracy.