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

Department of Dietetics and Nutrition Service, Asan Medical Center, University of Ulsan, Seoul, Korea.
Nutrition (Impact Factor: 2.93). 03/2012; 28(3):256-61. DOI: 10.1016/j.nut.2011.06.006
Source: PubMed


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.
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.
The 24HUNa and mean spot UNa values were significantly lower in patients with more advanced CKD (P = 0.006 and P < 0.001, respectively). One-time spot UNa was significantly higher in the evening than in the morning for patients with stage III, IV, or V CKD. Total sodium intake, but not sodium nutrient density (milligrams of sodium per 1000 kcal), was significantly different for patients with different stages of CKD (P = 0.001). The correlation coefficient between 24HUNa and mean spot UNa was 0.477 (95% confidence interval [CI] 0.384-0.562, P < 0.001), slightly higher than that between 24HUNa excretion and mean spot UNa/UCr (r = 0.313, 95% CI 0.207-0.465, P < 0.001). There was a linear relation between spot UNa and 24HUNa: mean spot UNa = 0.27 × 24HUNa + 60. Therefore, a 24HUNa excretion of 87 mEq (sodium intake 2 g/d) corresponded to a mean spot UNa level of 83 mEq/L. The correlation coefficient between sodium intake and mean spot UNa was 0.435 (95% CI 0.336-0.524, P < 0.001), significantly higher than that between sodium intake and mean spot UNa/UCr (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.
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.

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    • "Although, 24-hour urine sampling is more accurate in comparison with spot urine sampling, the last method can be used in epidemiological studies.[1013] Spot urine sodium-to-potassium ratio (Na/K) has been also used in evaluating dietary Na restriction in cirrhotic patients,[14] and in chronic kidney diseases patients to evaluate their Na intake.[715] Some studies reported high salt intake in young children of Western countries. "
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    ABSTRACT: This study aimed to assess the salt intake of Iranian children, and to assess the correlation of urinary electrolytes excretion with blood pressure. This cross-sectional study was conducted in 2011-2012 among 3-10-year-old children, selected by multi-stage cluster sampling from urban and rural areas of Isfahan, Iran. The sodium (Na), potassium (K), and creatinine (Cr) were measured in a random sample of the children's first morning fasting urine. Three-day averages of dietary intakes were analyzed by the Nutritionist-4 software. The mean (SD) of urinary Na was 177.17 (28.68) mEq/day without significant difference according to gender and living area. The mean (SD) dietary intakes of Na and K were 2017.76 (117.94) and 1119.06 (76.03) mg/day, respectively. Children of urban and rural areas consumed similar sources of salty foods (bread, cheese, and snacks) and had low intake of vegetables. No significant association was documented between urinary electrolytes excretions and blood pressure. This study, which to the best of our knowledge is the first of its kind in the Middle East and North Africa region, revealed that Iranian young children consume a large amount of sodium and small amount of potassium. The non-significant associations of electrolyte excretions with blood pressure may be because of the very young age group of participants. Given the development of preference to salt taste from early childhood, and the tracking of risk factors of chronic diseases from this age, reducing salt intake of young children should be emphasized.
    No preview · Article · Apr 2013 · International journal of preventive medicine
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    • "Kang et al. also compared spot urinary sodium to 24-hour urinary sodium excretion in 305 CKD patients, and found that the correlation between mean of three spot samples taken at different times of the day and 24-hour urinary sodium excretion was 0.477 (95% CI: 0.384–0.562; P < 0.01) for spot urinary sodium and 0.313 (0.207–0.415, <0.01) for spot urinary sodium to creatinine ratio [24]. However, these correlations, although significant, are weak and indicate associations rather than agreement. "
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    ABSTRACT: There is consistent evidence linking excessive dietary sodium intake to risk factors for cardiovascular disease and chronic kidney disease (CKD) progression in CKD patients; however, additional research is needed. In research trials and clinical practice, implementing and monitoring sodium intake present significant challenges. Epidemiological studies have shown that sodium intake remains high, and intervention studies have reported varied success with participant adherence to a sodium-restricted diet. Examining barriers to sodium restriction, as well as factors that predict adherence to a low sodium diet, can aid researchers and clinicians in implementing a sodium-restricted diet. In this paper, we critically review methods for measuring sodium intake with a specific focus on CKD patients, appraise dietary adherence, and factors that have optimized sodium restriction in key research trials and discuss barriers to sodium restriction and factors that must be considered when recommending a sodium-restricted diet.
    Full-text · Article · Dec 2012 · International Journal of Nephrology
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    • "Due to the increased participant burden involved in 24-hour urine collection, 24 hr collections (at baseline and all follow up points) will be supplemented with mid-stream urine collections occurring weekly in Phase 1 and at follow up points in Phase 2 (see Figure 2). Mid-stream urinary sodium has recently been demonstrated to have good agreement with 24-hour urinary sodium in CKD [53,54], and the collection of 24-hour samples concurrently with mid-stream samples will allow for further exploration of the agreement between these measures. Mid-stream urine samples will be analyzed for sodium, creatinine and albumin concentrations (Figure 3). "
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    ABSTRACT: Background Despite evidence implicating dietary sodium in the pathogenesis of cardiovascular disease (CVD) in chronic kidney disease (CKD), quality intervention trials in CKD patients are lacking. This study aims to investigate the effect of reducing sodium intake on blood pressure, risk factors for progression of CKD and other cardiovascular risk factors in CKD. Methods/design The LowSALT CKD study is a six week randomized-crossover trial assessing the effect of a moderate (180 mmol/day) compared with a low (60 mmol/day) sodium intake on cardiovascular risk factors and risk factors for kidney function decline in mild-moderate CKD (stage III-IV). The primary outcome of interest is 24-hour ambulatory blood pressure, with secondary outcomes including arterial stiffness (pulse wave velocity), proteinuria and fluid status. The randomized crossover trial (Phase 1) is supported by an ancillary trial (Phase 2) of longitudinal-observational design to assess the longer term effectiveness of sodium restriction. Phase 2 will continue measurement of outcomes as per Phase 1, with the addition of patient-centered outcomes, such as dietary adherence to sodium restriction (degree of adherence and barriers/enablers), quality of life and taste assessment. Discussion The LowSALT CKD study is an investigator-initiated study specifically designed to assess the proof-of-concept and efficacy of sodium restriction in patients with established CKD. Phase 2 will assess the longer term effectiveness of sodium restriction in the same participants, enhancing the translation of Phase 1 results into practice. This trial will provide much-needed insight into sodium restriction as a treatment option to reduce risk of CVD and CKD progression in CKD patients. Trial registration Universal Trial Number: U1111-1125-2149. Australian New Zealand Clinical Trials Registry Number: ACTRN12611001097932
    Full-text · Article · Oct 2012 · BMC Nephrology
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