Abstract
BackgroundHigh salt intake in patients with chronic kidney disease (CKD) may cause high blood pressure and increased albuminuria. Although, the estimation of salt intake is essential, there are no easy methods to estimate real salt intake.MethodsSalt intake was assessed by determining urinary sodium excretion from the collected urine samples. Estimation of salt intake by spot urine was calculated by Tanaka’s formula. The correlation between estimated and measured sodium excretion was evaluated by Pearson´s correlation coefficients. Performance of equation was estimated by median bias, interquartile range (IQR), proportion of estimates within 30% deviation of measured sodium excretion (P30) and root mean square error (RMSE).The sensitivity and specificity of estimated against measured sodium excretion were separately assessed by receiver-operating characteristic (ROC) curves.ResultsA total of 334 urine samples from 96 patients were examined. Mean age was 58 ± 16 years, and estimated glomerular filtration rate (eGFR) was 53 ± 27 mL/min. Among these patients, 35 had CKD stage 1 or 2, 39 had stage 3, and 22 had stage 4 or 5. Estimated sodium excretion significantly correlated with measured sodium excretion (R = 0.52, P < 0.01). There was apparent correlation in patients with eGFR <30 mL/min (R = 0.60, P < 0.01). Moreover, IQR was lower and P30 was higher in patients with eGFR < 30 mL/min. Estimated sodium excretion had high accuracy to predict measured sodium excretion, especially when the cut-off point was >170 mEq/day (AUC 0.835).ConclusionsThe present study demonstrated that spot urine can be used to estimate sodium excretion, especially in patients with low eGFR.
Highlights
High salt intake in patients with chronic kidney disease (CKD) may cause high blood pressure and increased albuminuria
The purpose of the present study was to evaluate whether the estimation of salt intake from spot urine could predict real salt intake in patients with CKD
Salt intake was assessed by determining urinary sodium excretion from the collected urine samples
Summary
High salt intake in patients with chronic kidney disease (CKD) may cause high blood pressure and increased albuminuria. High salt intake in CKD patients may cause high blood pressure, increased albuminuria and increased filtration fraction [2,3,4,5,6,7]. The INTERSALT study [11] estimated salt intake by 24 h urine collection at 52 centers in 32 countries, and showed that the mean daily salt intake was 9.2 g. The average estimated salt intake by 24 h urine collection obtained from 3 Japanese centers was 11.0 g, suggesting that the Japanese have a relatively higher than average salt intake.
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