title: Lipid and Creatinine Adjustment to Evaluate Health Effects of Environmental Exposures.
abstract: Urine- and serum-based biomarkers are useful for assessing individuals' exposure to environmental factors. However, variations in urinary creatinine (a measure of dilution) or serum lipid levels, if not adequately corrected for, can directly impact biomarker concentrations and bias exposure-disease association measures.
  
  
  
  Recent methodological literature has considered the complex relationships between creatinine or serum lipid levels, exposure biomarkers, outcomes, and other potentially relevant factors using directed acyclic graphs and simulation studies. The optimal measures of urinary dilution and serum lipids have also been investigated. Existing evidence supports the use of covariate-adjusted standardization plus creatinine adjustment for urinary biomarkers and standardization plus serum lipid adjustment for lipophilic, serum-based biomarkers. It is unclear which urinary dilution measure is best, but all serum lipid measures performed similarly. Future research should assess methods for pooled biomarkers and for studying diseases and exposures that affect creatinine or serum lipids directly.
authors.affiliation: Biostatistics and Computational Biology Branch, National Institute of Environmental Health Sciences, 111 TW Alexander Dr, Research Triangle Park, Durham, NC, 27709, USA. obrienkm2@niehs.nih.gov.
authors.forename: Katie M
authors.initials: KM
authors.lastname: O'Brien
authors.affiliation: Epidemiology Branch, National Institute of Environmental Health Sciences, National Institutes of Health, 111 TW Alexander Dr, Research Triangle Park, Durham, NC, 27709, USA.
authors.forename: Kristen
authors.initials: K
authors.lastname: Upson
authors.affiliation: Department of Environmental Health and Engineering, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
authors.forename: Jessie P
authors.initials: JP
authors.lastname: Buckley
mesh_terms: D015415:Biomarkers / Q000097:blood / Q000652:urine; D003404:Creatinine / Q000652:urine*; D004781:Environmental Exposure; D004784:Environmental Monitoring / Q000379:methods*; D004785:Environmental Pollutants; D006801:Humans; D008055:Lipids / Q000097:blood*
chemical_list: D015415:Biomarkers; D004785:Environmental Pollutants; D008055:Lipids; D003404:Creatinine
keywords: Biomarkers; Creatinine adjustment; Environmental exposures; Lipid adjustment