PDF(Pubmed)
Abstract：
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/m2), 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.
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/m2), 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.
摘要：
背景：在24小时尿液收集中测量的钠和钾通常用作参考测量，以验证自我报告的饮食摄入工具。
目的：为了评估在一天中指定时间收集和分析有限数量的尿液空隙（“定时空隙”）是否可以提供替代参考测量，并确定它们的最佳数量和时间。
方法：我们使用了441名年龄在18-39岁的成年人的尿液校准研究数据。参与者在单独的容器中收集每个尿液24小时，并记录收集时间。在同一天,他们使用24小时召回报告了饮食摄入量。在24小时复合样品和4个定时空隙（早上，下午,晚上，和隔夜）。使用线性回归模型来开发方程，使用4个单个定时空隙中的每一个来预测对数转换的24小时尿钠或钾水平，6对,4个三倍。等式还包括年龄，性别,种族,BMI(kg/m2),和对数肌酐。选择了最小化均方预测误差的最优组合，然后将观察到的和预测的24小时水平用作参考指标，以估计24小时饮食回忆的群体偏差和衰减因素。对这些估计进行了比较。
结果：发现的最佳组合如下：单个空隙-晚上；配对空隙-下午+过夜（钠）和早晨+晚上（钾）；三重空隙-早晨+晚上+过夜（钠）和早晨+下午+晚上（钾）。预测的24小时尿水平估计的24小时回忆组偏差和衰减因素没有明显的偏差，但精度低于观察到的24小时尿水平。为了恢复丢失的精度，据估计，单个空隙的样本量需要增加2.6-2.7倍，成对空隙的1.7-2.1倍，和1.5-1.6倍的三重空隙。
结论：我们的结果为进一步开发基于定时空隙的新参考生物标志物提供了基础。
背景：clinicaltrials.gov作为NCT01631240。
目的：为了评估在一天中指定时间收集和分析有限数量的尿液空隙（“定时空隙”）是否可以提供替代参考测量，并确定它们的最佳数量和时间。
方法：我们使用了441名年龄在18-39岁的成年人的尿液校准研究数据。参与者在单独的容器中收集每个尿液24小时，并记录收集时间。在同一天,他们使用24小时召回报告了饮食摄入量。在24小时复合样品和4个定时空隙（早上，下午,晚上，和隔夜）。使用线性回归模型来开发方程，使用4个单个定时空隙中的每一个来预测对数转换的24小时尿钠或钾水平，6对,4个三倍。等式还包括年龄，性别,种族,BMI(kg/m2),和对数肌酐。选择了最小化均方预测误差的最优组合，然后将观察到的和预测的24小时水平用作参考指标，以估计24小时饮食回忆的群体偏差和衰减因素。对这些估计进行了比较。
结果：发现的最佳组合如下：单个空隙-晚上；配对空隙-下午+过夜（钠）和早晨+晚上（钾）；三重空隙-早晨+晚上+过夜（钠）和早晨+下午+晚上（钾）。预测的24小时尿水平估计的24小时回忆组偏差和衰减因素没有明显的偏差，但精度低于观察到的24小时尿水平。为了恢复丢失的精度，据估计，单个空隙的样本量需要增加2.6-2.7倍，成对空隙的1.7-2.1倍，和1.5-1.6倍的三重空隙。
结论：我们的结果为进一步开发基于定时空隙的新参考生物标志物提供了基础。
背景：clinicaltrials.gov作为NCT01631240。
