title: Reliability of plasma fibroblast growth factor 23 as risk biomarker in epidemiological studies measured over a four-month period.
abstract: BACKGROUND
  Identified as a biomarker of altered calcium-phosphorus metabolism in chronic kidney disease, fibroblast growth factor 23 (FGF-23) can also be used as a biomarker of risk for cardiovascular disease in the general population. However, it is crucial to first evaluate the reproducibility (reliability) of plasma FGF-23 concentrations.
  
  
  METHODS
  We assessed the reliability of plasma FGF-23 concentrations using replicate blood samples taken four months apart of 207 participants from the European Prospective Investigation into Cancer and Nutrition-Potsdam Study.
  
  
  RESULTS
  Plasma FGF-23 concentrations at baseline (geometric mean: 24.7 RU/mL; 95% confidence interval [CI] in RU/mL: 21.8-27.9) were not significantly different from those measured four months later (geometric mean: 23.7 RU/mL; 95% CI in RU/mL: 20.6-27.1; P = 0.42). The intraclass correlation coefficients were 0.69 (95% CI: 0.62-0.76) for all; 0.64 (95% CI: 0.50-0.75) for men and 0.73 (95% CI: 0.64-0.81) for women.
  
  
  CONCLUSIONS
  Plasma FGF-23 concentrations showed good reliability over time. Our findings suggest that in epidemiological studies, a single plasma FGF-23 measurement may be sufficient to derive the relative risk in prospective cohort studies.
authors.affiliation: German Institute of Human Nutrition Potsdam-Rehbrücke, Department of Epidemiology, Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany. romina.digiuseppe@dife.de
authors.forename: Romina
authors.initials: R
authors.lastname: di Giuseppe
authors.forename: Frank
authors.initials: F
authors.lastname: Hirche
authors.forename: Jukka
authors.initials: J
authors.lastname: Montonen
authors.forename: Brian
authors.initials: B
authors.lastname: Buijsse
authors.forename: Jutta
authors.initials: J
authors.lastname: Dierkes
authors.forename: Gabriele I
authors.initials: GI
authors.lastname: Stangl
authors.forename: Heiner
authors.initials: H
authors.lastname: Boeing
authors.forename: Cornelia
authors.initials: C
authors.lastname: Weikert
mesh_terms: D015415:Biomarkers / Q000097:blood; D002318:Cardiovascular Diseases / Q000175:diagnosis* / Q000453:epidemiology*; D005260:Female; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000097:blood*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012307:Risk Factors; D012737:Sex Factors
chemical_list: D015415:Biomarkers; C000717427:FGF23 protein, human; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23