title: Urinary iodine excretion (UIE) estimated by iodine/creatinine ratio from spot urine in Chinese school-age children.
abstract: OBJECTIVE
  To assess the validity of urinary iodine excretion (UIE) estimated by urinary iodine/creatinine ratio (UI/Cr) from spot urines in Chinese school-age children.
  
  
  METHODS
  A cross-sectional survey was performed in which twice-repeated collections of 24-h urine, and spot urine samples were obtained within 1 month.
  
  
  METHODS
  Urinary iodine concentration (UIC), urinary creatinine concentration (UCr), urine volume (Uvol) of spot and 24-h urine samples were measured. Measured 24-h UIE was calculated from 24-h UIC multiplied by 24-h Uvol, while the estimated 24-h UIE was calculated from spot UI/Cr multiplied by 24-h urinary creatinine excretion (24-h UCrE).
  
  
  RESULTS
  No significant difference was observed in 24-h Uvol between two repeated collections (P = 0·70), while spot UIC, 24-h UIC, spot UI/Cr and measured 24-h UIE were significantly different (P < 0·05). The estimated 24-h UIE was 247 (136-431) μg/day in the first collection, lower than the measured 24-h UIE of 329 (183-536) μg/day (P < 0·001), while no significant difference was observed (P = 0·30) in the second sampling as the estimated 24-h UIE was 355 (168-624) μg/day and the measured 24-h UIE 350 (181-615) μg/day. The spot UIC (r = 0·57, P < 0·001), spot UI/Cr (r = 0·63, P < 0·001) and the estimated 24-h UIE (r = 0·83, P < 0·001) were strongly correlated with the measured 24-h UIE in the first collection. Likewise, in the second sampling, spot UIC (r = 0·60, P < 0·001), spot UI/Cr (r = 0·72, P < 0·001) and the estimated 24-h UIE (r = 0·89, P < 0·001) were also correlated with measured 24-h UIE. The Bland-Altman results indicated 95% of subjects were expected to locate within the limits of agreement (LOA), but showed an underestimation of the urinary iodine excretion by the estimated 24-h UIE. In addition, moderate-to-good agreement was found for the estimated and measured 24-h UIE, with kappa values of 0·55 and 0·66.
  
  
  CONCLUSIONS
  Estimated 24-h UIE by UI/Cr ratio from spot urine could represent a valid and reliable alternative for measured 24-h UIE in estimating iodine excretion in children.
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China.
authors.forename: Wen
authors.initials: W
authors.lastname: Chen
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China.
authors.forename: Xiang
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China.
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Guo
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Shen
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China.
authors.forename: Long
authors.initials: L
authors.lastname: Tan
authors.affiliation: Tianjin Institution of Endocrinology, Tianjin Medical University, Tianjin, China.
authors.forename: Laixiang
authors.initials: L
authors.lastname: Lin
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China.
authors.forename: Yalan
authors.initials: Y
authors.lastname: Wu
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China.
authors.forename: Wenqiang
authors.initials: W
authors.lastname: Wang
authors.affiliation: The Shandong Institute for Endemic Disease Control and Research, Shandong, China.
authors.forename: Jianchao
authors.initials: J
authors.lastname: Bian
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China.
authors.forename: Wanqi
authors.initials: W
authors.lastname: Zhang
mesh_terms: D002648:Child; D002681:China; D003404:Creatinine / Q000652:urine; D003430:Cross-Sectional Studies; D006801:Humans; D007455:Iodine / Q000652:urine*; D015203:Reproducibility of Results; D013048:Specimen Handling; D013997:Time Factors
chemical_list: D007455:Iodine; D003404:Creatinine