title: Exposure Classification and Temporal Variability in Urinary Bisphenol A Concentrations among Couples in Utah--The HOPE Study.
abstract: BACKGROUND
  Bisphenol A (BPA) is an endocrine disruptor and potential reproductive toxicant, but results of epidemiologic studies have been mixed and have been criticized for inadequate exposure assessment that often relies on a single measurement.
  
  
  OBJECTIVE
  Our goal was to describe the distribution of BPA concentrations in serial urinary specimens, assess temporal variability, and provide estimates of exposure classification when randomly selected samples are used to predict average exposure.
  
  
  METHODS
  We collected and analyzed 2,614 urine specimens from 83 Utah couples beginning in 2012. Female participants collected daily first-morning urine specimens during one to two menstrual cycles and male partners collected specimens during the woman's fertile window for each cycle. We measured urinary BPA concentrations and calculated geometric means (GM) for each cycle, characterized the distribution of observed values and temporal variability using intraclass correlation coefficients, and performed surrogate category analyses to determine how well repeat samples could classify exposure.
  
  
  RESULTS
  The GM urine BPA concentration was 2.78 ng/mL among males and 2.44 ng/mL among females. BPA had a high degree of variability among both males (ICC = 0.18; 95% CI: 0.11, 0.26) and females (ICC = 0.11; 95% CI: 0.08, 0.16). Based on our more stringent surrogate category analysis, to reach proportions ≥ 0.80 for sensitivity, specificity, and positive predictive value (PPV) among females, 6 and 10 repeat samples for the high and low tertiles, respectively, were required. For the medium tertile, specificity reached 0.87 with 10 repeat samples, but even with 11 samples, sensitivity and PPV did not exceed 0.36. Five repeat samples, among males, yielded sensitivity and PPV values ≥ 0.75 for the high and low tertiles, but, similar to females, classification for the medium tertile was less accurate.
  
  
  CONCLUSIONS
  Repeated urinary specimens are required to characterize typical BPA exposure.
  
  
  BACKGROUND
  Cox KJ, Porucznik CA, Anderson DJ, Brozek EM, Szczotka KM, Bailey NM, Wilkins DG, Stanford JB. 2016. Exposure classification and temporal variability in urinary bisphenol A concentrations among couples in Utah-the HOPE study. Environ Health Perspect 124:498-506; http://dx.doi.org/10.1289/ehp.1509752.
authors.affiliation: Office of Cooperative Reproductive Health, Division of Public Health, University of Utah, Salt Lake City, Utah, USA.
authors.forename: Kyley J
authors.initials: KJ
authors.lastname: Cox
authors.forename: Christina A
authors.initials: CA
authors.lastname: Porucznik
authors.forename: David J
authors.initials: DJ
authors.lastname: Anderson
authors.forename: Eric M
authors.initials: EM
authors.lastname: Brozek
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Szczotka
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Bailey
authors.forename: Diana G
authors.initials: DG
authors.lastname: Wilkins
authors.forename: Joseph B
authors.initials: JB
authors.lastname: Stanford
mesh_terms: D000293:Adolescent; D000328:Adult; D001559:Benzhydryl Compounds / Q000652:urine*; D052244:Endocrine Disruptors / Q000652:urine; D004781:Environmental Exposure; D004784:Environmental Monitoring; D004785:Environmental Pollutants / Q000652:urine*; D005191:Family Characteristics; D005260:Female; D006801:Humans; D008297:Male; D008597:Menstrual Cycle; D010636:Phenols / Q000652:urine*; D011897:Random Allocation; D013997:Time Factors; D000098826:Bisphenol A Compounds
chemical_list: D001559:Benzhydryl Compounds; D052244:Endocrine Disruptors; D004785:Environmental Pollutants; D010636:Phenols; C006780:bisphenol A; D000098826:Bisphenol A Compounds