Als C, Minder C, Willems D, Van Thi H V, Gerber H, Bourdoux P
Institute of Pathology, Inselspital, University of Bern, Bern, Switzerland.
Eur J Clin Nutr. 2003 Sep;57(9):1181-8. doi: 10.1038/sj.ejcn.1601740.
To compare different possibilities of reporting the iodine supply in the same urine samples. Indeed, in field studies, urinary iodine concentration (I/L: micro g I/L, micro mol I/L, I/creatinine: micro g I/g creatanine, micro mol I/mol creatinine) is more readily available than excretion (I/24h micro g I/24 h, micro mol I/24h). However, confusion exists regarding the comparability of iodine supply based upon I/L, I/creatinine and I/24h, which for decades have been regarded as biochemically equivalent.
We compared I/24h, I/L and I/creatinine in accurate 24 h collections of urine and I/L and I/creatinine in 47 spot urine samples.
A total of 13 subjects (Bern n=7, Brussels n=6) collected a total of 110 precise 24 h urine collections (Bern n=63, Brussels n=47). The subjects from Brussels also took a spot sample at the beginning of each 24 h collection.
Iodine supply in both places was mildly deficient according to the criteria of WHO; all but one collection indicated an intake of >0.39 micro mol I/24h (>50 micro g I/24h). The same data presented as I/creatinine (or I/L) indicated an iodine intake of <0.39 (<50 micro g I/24h) in 5% (24%) of the samples in Bern and 23% (57%) in Brussels. Similar findings were observed for 47 spot samples. Whatever the cut-off selected, I/creatinine and I/L were systematically lower than I/24h (P<0.0002). Creatinine showed smaller CV than volume but did not perform better in defining iodine intake.
Considering I/24h as a reference, both I/creatinine and I/L clearly underestimate the iodine intake in subjects with adequate proteoenergetic intake. The significant deviations observed illustrate the urgent need for establishing separate ranges for I/24h, I/creatinine and I/L. In population studies, these deviations might even be larger.
比较对同一尿液样本中碘供应情况进行报告的不同可能性。实际上，在现场研究中，尿碘浓度（I/L：微克碘/升、微摩尔碘/升，I/肌酐：微克碘/克肌酐、微摩尔碘/摩尔肌酐）比排泄量（I/24小时：微克碘/24小时、微摩尔碘/24小时）更容易获得。然而，基于I/L、I/肌酐和I/24小时的碘供应可比性存在混淆，几十年来它们一直被视为生化等效。
我们比较了准确收集的24小时尿液中的I/24小时、I/L和I/肌酐，以及47份随机尿液样本中的I/L和I/肌酐。
共有13名受试者（伯尔尼7名，布鲁塞尔6名）总共收集了110份精确的24小时尿液样本（伯尔尼63份，布鲁塞尔47份）。来自布鲁塞尔的受试者在每次24小时收集开始时还采集了一份随机样本。
根据世界卫生组织的标准，两地的碘供应均轻度不足；除一份样本外，所有收集样本均表明碘摄入量>0.39微摩尔碘/24小时（>50微克碘/24小时）。以I/肌酐（或I/L）表示的相同数据显示，在伯尔尼5%（24%）的样本以及布鲁塞尔23%（57%）的样本中碘摄入量<0.39（<50微克碘/24小时）。对47份随机样本也观察到了类似结果。无论选择何种临界值，I/肌酐和I/L都系统性地低于I/24小时（P<0.0002）。肌酐的变异系数比尿量小，但在确定碘摄入量方面表现并不更好。
以I/24小时为参考，I/肌酐和I/L均明显低估了蛋白质能量摄入充足的受试者的碘摄入量。观察到的显著偏差表明迫切需要为I/24小时、I/肌酐和I/L建立单独的范围。在人群研究中，这些偏差可能更大。
