Information Management Services Inc., Rockville, MD, United States; Biostatistics and Biomathematics Unit, Gertner Institute for Epidemiology and Health Policy Research, Chaim Sheba Medical Center, Ramat Gan, Israel.
Division of Health and Nutrition Examination Surveys, National Center for Health Statistics, Centers for Disease Control and Prevention, Hyattsville, MD, United States.
Am J Clin Nutr. 2024 May;119(5):1321-1328. doi: 10.1016/j.ajcnut.2024.02.013. Epub 2024 Feb 23.
Sodium and potassium measured in 24-h urine collections are often used as reference measurements to validate self-reported dietary intake instruments.
To evaluate whether collection and analysis of a limited number of urine voids at specified times during the day ("timed voids") can provide alternative reference measurements, and to identify their optimal number and timing.
We used data from a urine calibration study among 441 adults aged 18-39 y. Participants collected each urine void in a separate container for 24 h and recorded the collection time. For the same day, they reported dietary intake using a 24-h recall. Urinary sodium and potassium were analyzed in a 24-h composite sample and in 4 timed voids (morning, afternoon, evening, and overnight). Linear regression models were used to develop equations predicting log-transformed 24-h urinary sodium or potassium levels using each of the 4 single timed voids, 6 pairs, and 4 triples. The equations also included age, sex, race, BMI (kg/m), and log creatinine. Optimal combinations minimizing the mean squared prediction error were selected, and the observed and predicted 24-h levels were then used as reference measures to estimate the group bias and attenuation factors of the 24-h dietary recall. These estimates were compared.
Optimal combinations found were as follows: single voids-evening; paired voids-afternoon + overnight (sodium) and morning + evening (potassium); and triple voids-morning + evening + overnight (sodium) and morning + afternoon + evening (potassium). Predicted 24-h urinary levels estimated 24-h recall group biases and attenuation factors without apparent bias, but with less precision than observed 24-h urinary levels. To recover lost precision, it was estimated that sample sizes need to be increased by ∼2.6-2.7 times for a single void, 1.7-2.1 times for paired voids, and 1.5-1.6 times for triple voids.
Our results provide the basis for further development of new reference biomarkers based on timed voids.
clinicaltrials.gov as NCT01631240.
24 小时尿液收集测量的钠和钾常被用作验证自我报告饮食摄入仪器的参考测量值。
评估在一天中特定时间收集和分析有限数量的尿液（“定时排空”）是否可以提供替代的参考测量值，并确定其最佳数量和时间。
我们使用了来自 441 名 18-39 岁成年人尿液校准研究的数据。参与者将每个尿液样本收集在单独的容器中 24 小时，并记录收集时间。在同一天，他们使用 24 小时回忆法报告饮食摄入情况。尿液中的钠和钾在 24 小时混合样本和 4 个定时排空（清晨、下午、晚上和夜间）中进行分析。使用线性回归模型，根据每个 4 个单独的定时排空、6 对和 4 个三重排空，开发预测对数转换的 24 小时尿液钠或钾水平的方程。这些方程还包括年龄、性别、种族、BMI（kg/m）和尿肌酐的对数。选择最小化均方预测误差的最佳组合，然后使用观察到的和预测的 24 小时水平作为参考测量值来估计 24 小时饮食回忆的组偏倚和衰减因子。对这些估计值进行了比较。
发现的最佳组合如下：单排空-晚上；双排空-下午+夜间（钠）和早上+晚上（钾）；和三排空-早上+晚上+夜间（钠）和早上+下午+晚上（钾）。预测的 24 小时尿液水平估计 24 小时回忆组偏倚和衰减因子没有明显的偏差，但精度低于观察到的 24 小时尿液水平。为了恢复失去的精度，估计需要将单个排空的样本量增加约 2.6-2.7 倍，双排空的样本量增加 1.7-2.1 倍，三排空的样本量增加 1.5-1.6 倍。
我们的结果为进一步开发基于定时排空的新参考生物标志物提供了基础。
clinicaltrials.gov 为 NCT01631240。
