Abstract
Objective: The most accurate way to measure urinary iodine excretion in epidemiological surveys is still debated. We propose a new principle of estimating iodine excretion based on casual urine samples.
Material and methods: A total of 123 24 h urine samples and corresponding casual urine samples were collected from 31 subjects. Iodine excretion was expressed as 24 h iodine excretion and three different estimates: iodine concentration in the casual sample, iodine/gram creatinine in the casual sample, and the new principle—iodine/creatinine ratio in the casual sample, adjusted for expected creatinine excretion of the individual.
Results: All three estimates based on casual urine samples correlated significantly to 24 h values with a r (Pearson) of 0.37 for iodine concentration, 0.61 for iodine/creatinine ratio and 0.62 for the age- and sex-adjusted iodine/creatinine ratio. The median iodine excretion in the entire group was 143 μg/day in 24 h samples, 87 μg/l as iodine concentration, 77 μg/g creatinine as iodine/creatinine ratio and 126 μg/day as age- and sex-adjusted iodine/creatinine ratio.
Conclusion: Age- and sex-adjusted iodine/creatinine ratio is a more accurate and unbiased estimate of iodine excretion in epidemiological surveys of adults than the two most frequently used estimated: iodine concentration and iodine/gram creatinine, as these two estimates may introduce a bias depending on the composition of the investigated group. The adjusted iodine/creatinine ratio is superior to the other estimates, especially when individual estimates of 24 h iodine excretion is required or cohorts of selected groups are investigated.
Sponsorship: This work was supported by grants from the Medical Research Foundation Region Greater Copenhagen, Faroe Islands and Greenland; the Wedell-Wedellsborg Foundation; Musikforlæggerne Agnes and Knut Mørks Foundation.
European Journal of Clinical Nutrition (2000) 54, 361–363
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Guarantor: N Knudsen
Contributors: NK participated in planning the study, collecting data, pro-cessing of data and preparation of the manuscript. EC was responsible for the analysis of urine samples. MB-C and BN participated in planning the study, collecting data and preparing the manuscript. HP participated in planning the study and preparing the manuscript.
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Knudsen, N., Christiansen, E., Brandt-Christensen, M. et al. Age- and sex-adjusted iodine/creatinine ratio. A new standard in epidemiological surveys? Evaluation of three different estimates of iodine excretion based on casual urine samples and comparison to 24 h values. Eur J Clin Nutr 54, 361–363 (2000). https://doi.org/10.1038/sj.ejcn.1600935
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DOI: https://doi.org/10.1038/sj.ejcn.1600935
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