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Variability of urinary cadmium excretion in spot urine samples, first morning voids, and 24 h urine in a healthy non-smoking population: Implications for study design

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Author

  • Magnus Akerstrom
  • Lars Barregard
  • Thomas Lundh
  • Gerd Sallsten

Summary, in English

When selecting the least biased exposure surrogate, for example, the concentration of a biomarker in a urine sample, information on variability must be taken into consideration. We used mixed-effects models to estimate the variability and determinants of urinary cadmium (U-Cd) excretion using spot urine samples collected at six fixed times during 2 days about 1 week apart, from 24 healthy non-smokers. The urine samples were analysed for U-Cd, the concentrations were adjusted for dilution, and the excretion rates were calculated. Between-individual variability dominated the total variability for most measures of U-Cd excretion, especially for 24h urine and first morning samples. The U-Cd excretion showed a circadian rhythm during the day, and time point of sampling was a significant factor in the mixed-effects models, thus a standardised sampling time, such as first morning urine samples, needs to be applied. Gender, urinary flow rate, age, and urinary protein excretions were also significant determinants for U-Cd excretion. The choice of biomarker for U-Cd excretion was found to be more important in individually-based studies of exposure-response relationships than in studies of comparing Cd levels of groups. When planning a study, this variability of U-Cd in spot samples must be acknowledged.

Publishing year

2014

Language

English

Pages

171-179

Publication/Series

Journal of Exposure Science & Environmental Epidemiology

Volume

24

Issue

2

Document type

Journal article

Publisher

Nature Publishing Group

Topic

  • Environmental Health and Occupational Health

Keywords

  • variability
  • spot urine
  • urinary excretion
  • cadmium
  • 24h urine
  • study
  • design

Status

Published

ISBN/ISSN/Other

  • ISSN: 1559-064X