Perrine Cria G, Cogswell Mary E, Swanson Christine A, Sullivan Kevin M, Chen Te-Ching, Carriquiry Alicia L, Dodd Kevin W, Caldwell Kathleen L, Wang Chia-Yih
1 Division of Nutrition, Physical Activity, and Obesity, Centers for Disease Control and Prevention , Atlanta, Georgia .
Thyroid. 2014 Apr;24(4):748-57. doi: 10.1089/thy.2013.0404. Epub 2014 Mar 4.
Median urine iodine concentration (UIC; μg/L) in spot urine samples is recommended for monitoring population iodine status. Other common measures are iodine:creatinine ratio (I/Cr; μg/g) and estimated 24-hour urine iodine excretion (UIE; I/Cr × predicted 24-hour Cr; μg/day). Despite different units, these measures are often used interchangeably, and it is unclear how they compare with the reference standard 24-hour UIE.
Volunteers aged 18-39 years collected all their urine samples for 24 hours (n=400). Voids from morning, afternoon, evening, overnight, and a composite 24-hour sample were analyzed for iodine. We calculated median observed 24-hour UIE and 24-hour UIC, and spot UIC, I/Cr, and two measures of estimated UIE calculated using predicted 24-hour Cr from published estimates by Kesteloot and Joosens (varies by age and sex) and published equations by Mage et al. (varies by age, sex, race, and anthropometric measures). We examined mean differences and relative difference across iodine excretion levels using Bland-Altman plots.
Median 24-hour UIE was 173.6 μg/day and 24-hour UIC was 144.8 μg/L. From timed-spot urine samples, estimates were: UIC 147.3-156.2 μg/L; I/Cr 103.6-114.3 μg/g, estimated 24-hour UIE (Kesteloot and Joosens) 145.7-163.3 μg/day; and estimated 24-hour UIE (Mage) 176.5-187.7 μg/day. Iodine measures did not vary consistently by timing of spot urine collection. Compared with observed 24-hour UIE, on average, estimated (Mage) 24-hour UIE was not significantly different, while estimated 24-hour UIE (Kesteloot and Joosens) was significantly different for some ethnicity/sex groups. Compared with 24-hour UIC, on average, spot UIC did not differ.
Estimates of UIC, I/Cr, and estimated 24-hour UIE (I/Cr × predicted 24-hour Cr) from spot urine samples should not be used interchangeably. Estimated 24-hour UIE, where predicted 24-hour Cr varies by age, sex, ethnicity, and anthropometric measures and was calculated with prediction equations using data from the sample, was more comparable to observed 24-hour UIE than when predicted 24-hour Cr was from published estimates from a different population. However, currently no cutoffs exist to interpret population estimated 24-hour UIE values.
推荐采用即时尿样中的尿碘中位数浓度（UIC；μg/L）来监测人群碘营养状况。其他常用指标包括碘与肌酐比值（I/Cr；μg/g）以及估算的24小时尿碘排泄量（UIE；I/Cr×预测的24小时肌酐量；μg/天）。尽管这些指标的单位不同，但它们常被交替使用，目前尚不清楚它们与参考标准24小时UIE相比情况如何。
18 - 39岁的志愿者收集其24小时内的全部尿样（n = 400）。对晨尿、下午尿、晚尿、夜间尿以及混合的24小时尿样进行碘含量分析。我们计算了观察到的24小时UIE中位数和24小时UIC中位数，以及即时UIC、I/Cr，还有两种使用Kesteloot和Joosens发表的估算值（因年龄和性别而异）预测的24小时肌酐量计算得到的估算UIE指标，以及Mage等人发表的公式（因年龄、性别、种族和人体测量指标而异）计算得到的估算UIE指标。我们使用Bland - Altman图检查了不同碘排泄水平下的平均差异和相对差异。
24小时UIE中位数为173.6μg/天，24小时UIC为144.8μg/L。即时尿样的估算值为：UIC 147.3 - 156.2μg/L；I/Cr 103.6 - 114.3μg/g，估算的24小时UIE（Kesteloot和Joosens）145.7 - 163.3μg/天；估算的24小时UIE（Mage）176.5 - 187.7μg/天。碘指标在即时尿样采集时间上的变化并不一致。与观察到的24小时UIE相比，平均而言，估算的（Mage）24小时UIE无显著差异，而估算的24小时UIE（Kesteloot和Joosens）在某些种族/性别组中有显著差异。与24小时UIC相比，平均而言，即时UIC无差异。
即时尿样中UIC、I/Cr和估算的24小时UIE（I/Cr×预测的24小时肌酐量）的估算值不应交替使用。当预测的24小时肌酐量因年龄、性别、种族和人体测量指标而异，并使用样本数据通过预测方程计算时，估算的24小时UIE比使用来自不同人群的发表估算值计算预测的24小时肌酐量时，与观察到的24小时UIE更具可比性。然而，目前尚无用于解释人群估算的24小时UIE值的临界值。
