Relationship between Urine Creatinine and Urine Osmolality in Spot Samples among Men and Women in the Danish Diet Cancer and Health Cohort
Selinay Ozdemir,
Clara G. Sears,
James M. Harrington,
Aslak Harbo Poulsen,
Jessie Buckley,
Chanelle J. Howe,
Katherine A. James,
Anne Tjonneland,
Gregory A. Wellenius,
Ole Raaschou-Nielsen,
Jaymie Meliker
Affiliations
Selinay Ozdemir
Department of Biology, Stony Brook University, Stony Brook, NY 11794, USA
Clara G. Sears
Department of Epidemiology, Brown University School of Public Health, Providence, RI 02903, USA
James M. Harrington
Analytical Science Division, RTI International, Research Triangle Park, NC 27709, USA
Aslak Harbo Poulsen
Danish Cancer Society Research Center, 2100 Copenhagen, Denmark
Jessie Buckley
Departments of Environment Health and Engineering & Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
Chanelle J. Howe
Department of Epidemiology, Brown University School of Public Health, Providence, RI 02903, USA
Katherine A. James
Department of Environmental and Occupational Health, Colorado School of Public Health, University of Colorado-Anschutz Medical Campus, Denver, CO 80217, USA
Anne Tjonneland
Danish Cancer Society Research Center, 2100 Copenhagen, Denmark
Gregory A. Wellenius
Department of Epidemiology, Brown University School of Public Health, Providence, RI 02903, USA
Ole Raaschou-Nielsen
Danish Cancer Society Research Center, 2100 Copenhagen, Denmark
Jaymie Meliker
Program in Public Health, Department of Family, Population, & Preventive Medicine, Stony Brook University, Stony Brook, NY 11794, USA
Assays of urine biomarkers often use urine creatinine to account for urinary dilution, even though creatinine levels are influenced by underlying physiology and muscle catabolism. Urine osmolality—a measure of dissolved particles including ions, glucose, and urea—is thought to provide a more robust marker of urinary dilution but is seldom measured. The relationship between urine osmolality and creatinine is not well understood. We calculated correlation coefficients between urine creatinine and osmolality among 1375 members of a subcohort of the Danish Diet, Cancer, and Health Cohort, and within different subgroups. We used linear regression to relate creatinine with osmolality, and a lasso selection procedure to identify other variables that explain remaining variability in osmolality. Spearman correlation between urine creatinine and osmolality was strong overall (ρ = 0.90; 95% CI: 0.89–0.91) and in most subgroups. Linear regression showed that urine creatinine explained 60% of the variability in urine osmolality, with another 9% explained by urine thallium (Tl), cesium (Cs), and strontium (Sr). Urinary creatinine and osmolality are strongly correlated, although urine Tl, Cs, and Sr might help supplement urine creatinine for purposes of urine dilution adjustment when osmolality is not available.
