Nutrition Program, Federal University of São Paulo, São Paulo, Brazil.
Division of Nephrology, Pro-rim Foundation, Joinville, Brazil.
Nephron. 2019;143(4):255-263. doi: 10.1159/000502013. Epub 2019 Sep 5.
The assessment of sodium intake is difficult due to low accuracy of dietary records and to the inconvenience of 24-h urine collections. Therefore, equations based on spot urine samples have been proposed to estimate sodium intake. In this study, we aimed to develop and to validate equations to estimate 24-h urinary sodium excretion (24hUNa) from several urine samples in chronic kidney disease (CKD) patients.
Cross-sectional study with 76 CKD patients (males 55.3%; age: 64.5 [56.0-69.0] years; glomerular filtration rate 27.8 [24.7-32.1] mL/min). Sodium excretion was measured in 12-h daytime and 12-h nighttime collections; spot 1 (first urine of the day) and spot 2 (second urine of the day). By multivariable linear regression analysis, 4 equations were developed. The equations' accuracy was evaluated by P30 test. Association between estimated and measured 24hUNa was assessed by intraclass correlation coefficient (ICC); mean differences and limits of agreement by Bland-Altman plot. Data from 51 CKD patients of other CKD outpatient clinic were used to validate the equation developed from spot 2.
The 4 equations showed significant (p < 0.001) ICC and relatively good accuracy when compared to 24hUNa (Daytime: ICC = 0.89; P30 = 84%; Nighttime: ICC = 0.90; P30 = 83%; spot 1: ICC = 0.85; P30 = 78%; and spot 2: ICC = 0.70; P30 = 76%). In validation set, the equation from spot 2 was moderately accurate (P30 = 67%). Mean bias and ICC were 19.9 mmol/day and 0.58 (p = 0.001), respectively. A high sensitivity (97%) and specificity (89%) were found for a cutoff of 3.6 g of sodium/day.
Equations derived from 12 h collections better performed than spot urine when compared to gold standard 24hUNa. The equation from spot 2 showed good sensitivity to identify excessive sodium intake.
由于膳食记录准确性低以及 24 小时尿液收集不便，钠摄入量的评估较为困难。因此，已经提出了基于单次尿液样本的方程来估计钠摄入量。本研究旨在为慢性肾脏病（CKD）患者开发和验证能够从多个尿液样本中估计 24 小时尿钠排泄量（24hUNa）的方程。
横断面研究共纳入 76 名 CKD 患者（男性 55.3%；年龄：64.5[56.0-69.0]岁；肾小球滤过率 27.8[24.7-32.1]mL/min）。钠排泄量通过 12 小时日间和 12 小时夜间收集、单次晨尿（第 1 次晨尿）和单次第 2 次晨尿进行测量。通过多变量线性回归分析，开发了 4 个方程。通过 P30 测试评估方程的准确性。通过组内相关系数（ICC）评估估计的 24hUNa 与实测 24hUNa 之间的相关性；通过 Bland-Altman 图评估平均差异和一致性界限。使用另一家 CKD 门诊的 51 名 CKD 患者的数据来验证基于单次第 2 次晨尿的方程。
4 个方程与 24hUNa 相比均具有显著（p<0.001）的 ICC 和较好的准确性（日间：ICC=0.89；P30=84%；夜间：ICC=0.90；P30=83%；单次晨尿：ICC=0.85；P30=78%；单次第 2 次晨尿：ICC=0.70；P30=76%）。在验证组中，单次第 2 次晨尿的方程准确性中等（P30=67%）。平均偏倚和 ICC 分别为 19.9mmol/d 和 0.58（p=0.001）。对于 3.6g/d 的钠摄入量的截断值，检测的灵敏度为 97%，特异性为 89%。
与金标准 24hUNa 相比，12 小时收集的方程优于单次尿液样本。单次第 2 次晨尿的方程对于识别钠摄入过量具有较高的敏感性。
