title: The challenge of measuring circulating estradiol at low concentrations.
abstract: Demand for measuring estradiol at low concentrations is increasing, and the widely used 'direct' radioimmunoassays that do not require a preliminary organic purification step may be inadequate in patient care because of their limited accuracy. In observational epidemiology, however, the main concern is to obtain a correct ranking of individuals' hormone concentration relative to the true level (as determined through a 'gold standard'). Despite differences in the absolute scale of measured and true concentrations, correct ranking will permit calculation of unbiased estimates of hormone-disease associations. In prospective studies, the major concerns are the limited volume of often irreplaceable specimens and the need to perform a large number of assays within a reasonable period of time. Organic purification is often not feasible because of sample volume requirements and logistic difficulties, and so the development of accurate, rapid and inexpensive methods to measure sex steroids at low concentrations would represent a valuable new research tool for both clinicians and epidemiologists.
authors.affiliation: Division of Epidemiology, Department of Obstetrics and Gynecology, New York University School of Medicine, New York, USA. toniop01@med.nyu.edu
authors.forename: Paolo
authors.initials: P
authors.lastname: Toniolo
authors.forename: Annekatrin
authors.initials: A
authors.lastname: Lukanova
mesh_terms: D001943:Breast Neoplasms; D016021:Epidemiologic Studies; D004958:Estradiol / Q000097:blood*; D005260:Female; D006801:Humans; D011446:Prospective Studies; D011863:Radioimmunoassay / Q000592:standards*; D012016:Reference Values; D015203:Reproducibility of Results; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D013048:Specimen Handling
chemical_list: D004958:Estradiol
references.citation: J Natl Cancer Inst. 2002 Apr 17;94(8):606-16
references.pmid: 11959894
references.citation: Br J Cancer. 2001 Apr 6;84(7):975-81
references.pmid: 11286480
references.citation: Cancer Epidemiol Biomarkers Prev. 2001 Jul;10(7):757-65
references.pmid: 11440961
references.citation: Steroids. 2002 Mar;67(3-4):151-8
references.pmid: 11856538
references.citation: Breast Cancer Res. 2005;7(1):1-4
references.pmid: 15642174
references.citation: Cancer Epidemiol Biomarkers Prev. 2002 Oct;11(10 Pt 1):1065-71
references.pmid: 12376508
references.citation: Cancer Epidemiol Biomarkers Prev. 2003 Dec;12(12):1457-61
references.pmid: 14693737
references.citation: Cancer Epidemiol Biomarkers Prev. 1996 Nov;5(11):923-8
references.pmid: 8922302
references.citation: Cancer Epidemiol Biomarkers Prev. 1997 Jun;6(6):429-32
references.pmid: 9184776