title: Liquid chromatography tandem mass spectrometry assay for fast and sensitive quantification of estrone-sulfate.
abstract: BACKGROUND
  The circulating pool of estrone-sulfate is considered as a "reservoir" of slowly-metabolized estrogen that can be exploited for assessing overall individual estrogenicity. The aim of this study was to develop a rapid and sensitive liquid chromatography-tandem mass spectrometry assay for the determination of estrone-sulfate, suitable for routine clinical investigations.
  
  
  METHODS
  The proposed assay is based on a simple protein precipitation procedure and on a fast measurement with a triple-quadrupole mass spectrometer operating in negative ion mode and in multiple reaction monitoring. The method was assessed for intra- and inter-day precision, accuracy, recovery, and clinical suitability. A comparison with available radioimmunoassay was also performed.
  
  
  RESULTS
  The LC-MS/MS method is able to detect estrone-sulfate concentrations < or =1pg/mL and has a low limit of quantification of 7.8pg/mL. Intra- and inter-day precision and accuracy were less than 10.5% and 5.0% respectively. The recovery was in the range of 93%-110%. When compared with radioimmunoassay the method resulted more accurate and therefore more suitable for quantifying the estrone-sulfate in different clinical settings, including patients treated with aromatase inhibitors.
  
  
  CONCLUSIONS
  The proposed LC-MS/MS method represents a convincing alternative to the immunoassay for a fast, cost-effective and reliable measurement of estrone-sulfate in routine clinical investigations and in large epidemiological studies. It may contribute in shedding a new light on the diagnostic value of estrone-sulfate in normal and pathological conditions.
authors.affiliation: National Cancer Institute and Center for Molecular Biomedicine, Aviano, PN, Italy. giuseppe.corona@cro.it
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Corona
authors.forename: Caterina
authors.initials: C
authors.lastname: Elia
authors.forename: Bruno
authors.initials: B
authors.lastname: Casetta
authors.forename: Alessandro
authors.initials: A
authors.lastname: Da Ponte
authors.forename: Lino
authors.initials: L
authors.lastname: Del Pup
authors.forename: Enzo
authors.initials: E
authors.lastname: Ottavian
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Toffoli
mesh_terms: D001943:Breast Neoplasms / Q000097:blood* / Q000737:chemistry / Q000188:drug therapy; D002851:Chromatography, High Pressure Liquid; D004970:Estrone / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013431:Sulfates / Q000097:blood*; D053719:Tandem Mass Spectrometry
chemical_list: D013431:Sulfates; D004970:Estrone