title: Assay reproducibility and interindividual variation for 15 serum estrogens and estrogen metabolites measured by liquid chromatography-tandem mass spectrometry.
abstract: BACKGROUND
  Interindividual differences in estrogen metabolism may partially account for differences in risks of estrogen-responsive cancers. We conducted a proof-of-performance study to assess the reproducibility of a LC/MS-MS method for measurement of 15 serum estrogens and metabolites (all 15 termed EM) in total (conjugated+unconjugated) and unconjugated forms and describe interindividual variation.
  
  
  METHODS
  Interindividual variation in serum EM profiles was evaluated for 20 premenopausal women, 15 postmenopausal women, and 10 men. Replicate aliquots from 10 premenopausal women, 5 postmenopausal women, and 5 men were assayed eight times over 4 weeks. Components of variance were used to calculate coefficients of variation (CV) and intraclass correlation coefficients (ICC).
  
  
  RESULTS
  In postmenopausal women and men, median EM concentrations were similar and substantially lower than that in premenopausal women. Within each sex/menopausal group, the sum of all EM varied 5- to 7-fold across extreme deciles. Some EM had greater variation; total estrone varied approximately 12-fold in premenopausal and postmenopausal women. Unconjugated estradiol varied 17-fold in postmenopausal women but only 5-fold in premenopausal women and men. CVs reflecting variation across replicate measures for individuals were <5% for most EM, but higher in some individuals with a low EM concentration. Overall laboratory CVs for all but one EM were <2% and ICCs were >99% for all EM in each group.
  
  
  CONCLUSIONS
  The serum EM assay has excellent laboratory reproducibility. In premenopausal women, postmenopausal women, and men, interindividual variation in EM measures is substantially greater than laboratory variation.
  
  
  CONCLUSIONS
  The serum EM assay is suitable for epidemiologic application. See all the articles in this CEBP Focus section, "Biomarkers, Biospecimens, and New Technologies in Molecular Epidemiology."
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland. bjfuhrman@uams.edu.
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: Fuhrman
authors.affiliation: Laboratory of Proteomics and Analytical Technologies, Cancer Research Technology Program, Leidos Biomedical Research, Inc., Frederick National Laboratory for Cancer Research, Frederick, Maryland.
authors.forename: Xia
authors.initials: X
authors.lastname: Xu
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland.
authors.forename: Roni T
authors.initials: RT
authors.lastname: Falk
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland.
authors.forename: Cher M
authors.initials: CM
authors.lastname: Dallal
authors.affiliation: Laboratory of Proteomics and Analytical Technologies, Cancer Research Technology Program, Leidos Biomedical Research, Inc., Frederick National Laboratory for Cancer Research, Frederick, Maryland.
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Veenstra
authors.affiliation: Chemical Biology Laboratory, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, Maryland.
authors.forename: Larry K
authors.initials: LK
authors.lastname: Keefer
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland.
authors.forename: Barry I
authors.initials: BI
authors.lastname: Graubard
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland.
authors.forename: Louise A
authors.initials: LA
authors.lastname: Brinton
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland.
authors.forename: Regina G
authors.initials: RG
authors.lastname: Ziegler
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland.
authors.forename: Gretchen L
authors.initials: GL
authors.lastname: Gierach
mesh_terms: D002853:Chromatography, Liquid / Q000379:methods*; D004967:Estrogens / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D017698:Postmenopause; D017697:Premenopause; D015203:Reproducibility of Results; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D004967:Estrogens