Plasma estrone sulfate assay in men: Comparison of radioimmunoassay, mass spectrometry coupled to gas chromatography (GC–MS), and liquid chromatography-tandem mass spectrometry (LC-MS/MS)

BackgroundEstrogens are involved in the natural history of the prostate cancer and estrone sulfate, the quantitatively main circulating plasma estrogen in men, has been associated with an aggressive form of this cancer. A convenient and accurate plasma assay of this steroid has become important.MethodsWe simultaneously assayed estrone sulfate in the plasma of one hundred men aged 30–50 years, according to LC-MS/MS, GC–MS after solvolysis of E1S, radioimmunoassay after a chromatographic purification step, and a direct RIA commercial kit.ResultsEstrone sulfate plasma levels obtained with the first three methods were not significantly different. However, estrone sulfate levels measured by the direct RIA were three-fold higher than those obtained by the first three methods. We showed that the excessively high estrone sulfate levels obtained with the direct RIA kit had two origins: interference by high dehydroepiandrosterone sulfate plasma levels in men, and estrone sulfate inaccurate low concentrations in the standards.ConclusionThe LC-MS/MS method can be considered as an optimum option for clinical laboratory. The GC–MS method requires solvolysis to estrone, but allows simultaneous unconjugated steroid measurement. RIA method, with chromatographic purification, is cumbersome, but less expensive. DSL-5400 kit yielded estrone sulfate plasma levels that were too high.