Objective: To evaluate the validity of iodine/ereatinine ratio (UI/Cr) from spot urines in estimating 24-h urinary iodine excretion (24-h UIE) in school-age children.Design: A cross-sectional survey.Twice repeated collections of 24-h urine and morning spot urine samples were obtained within one month.24-h urinary iodine concentration (24-h UIC), 24-h urinary creatinine concentration (24-h U-Cr), 24-h urinary volume (24-h U-vol), morning spot urinary iodine concentration (MUIC) and morning spot urinary creatinine concentration (MU-Cr) were measured in all samples.Measured 24-h UIE was calculated by 24-h UIC multiplying 24-h U-vol, while estimated 24-h UIE was calculated by morning spot urinary iodine/creatinine ratio (MUI/Cr) multiplying 24-h urinary creatinine excretion (24-h UCrE).Setting: Ningjin and Lingxian Counties, Shandong, China.Subjects: 981 healthy school-age children Results: No significant differences were observed in MUI/Cr, 24-h UIC and measured 24-h UIE between twice repeated collections.MUI/Cr, 24-h UI/Cr and estimated 24-h UIE were strongly correlated with measured 24-h UIE.The Kappa value α was 0.615 in first collection and 0.599 in second one,demonstrating a good agreement between estimated and measured 24-h UIE.Estimated 24-h UIE was slightly lower than measured 24-h UIE in both collections.Measured 24-h UIE and estimated 24-h UIE were significantly correlated with age.However, no differences were observed in MUI/Cr and 24-h UI/Cr among different ages.Conclusions: Estimated 24-h UIE from morning spot urine could be a valid and reliable alternative for measured 24-h UIE from 24-h urine sample in evaluating individual iodine intake, even though there was 10%~14% underestimation.
24-h urine urinary iodine urinary creatinine iodine/creatinine ratio children
Wanqi Zhang Wen Chen Xiaohui Guo Jun Shen Long Tan Laixiang Lin Yan Ye Yalan Wu Wei Wang Wenqiang Wang Wen Jiang Jianchao Bian
Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University,Tianji Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University,Tianji Department of Sanitary Chemistry, School of Public Health, Tianjin Medical University, Tianjin,China Tianjin Institution of Endocrinology, Tianjin Medical University, Tianjin, China Shandong Institute for Endemic Disease Control and Research, Shandong Province, China