Use of mean spot urine sodium concentrations to estimate daily sodium intake in patients with chronic kidney disease

Abstract Objective Sodium intake is an important issue for patients with chronic kidney disease (CKD). The two most widely used methods to measure sodium are 24-h urinary sodium excretion (24HUNa), which can be difficult to perform routinely, and sodium intake by dietary recall, which can be inaccurate. This study evaluated use of the mean value of three spot urinary sodium (UNa) concentrations to estimate daily sodium intake in patients with CKD. Methods This cross-sectional study enrolled 305 patients with CKD, none of whom were on dialysis, who visited the nephrology clinic at the Asan Medical Center (Seoul, Korea). We performed three spot UNa tests, three calculations of the UNa/creatinine (UCr) ratio, one measurement of 24HUNa, and one measurement of sodium intake by dietary recall. Results The 24HUNa and mean spot UNa values were significantly lower in patients with more advanced CKD ( P = 0.006 and P P = 0.001). The correlation coefficient between 24HUNa and mean spot UNa was 0.477 (95% confidence interval [CI] 0.384–0.562, P r = 0.313, 95% CI 0.207–0.465, P P r = 0.197, 95% CI 0.091–0.301, P = 0.001). Mean spot UNa tended to be better correlated with 24HUNa than with sodium intake. Conclusion Mean spot UNa is a simple and effective method that can be used to monitor sodium intake in patients with CKD. A daily intake of 2 g of sodium corresponds to a mean spot UNa level of approximately 83 mEq/L in patients with CKD.