Formula to detect high sodium excretion from spot urine in chronic kidney disease patients / Fórmula para detectar elevada excreção de sódio a partir de amostra isolada de urina de pacientes com doença renal crônica pré-dialítica

Abstract Introduction: Excessive sodium intake is related to adverse renal and cardiovascular outcomes in patients with chronic kidney disease (CKD) and assessment of sodium intake is complex and not evaluated very often in clinical practice. Objective: To develop a new formula to estimate 24h sodium excretion from urine sample (second void) of patients with CKD. Methods: We included 51 participants with CKD who provided 24-hour urine collection and a sample of the second urine of the day to determine the sodium excretion. A formula to estimate the 24-hour sodium excretion was developed from a multivariate regression equation coefficients. The accuracy of the formula was tested by calculating the P30 (proportion of estimates within 30% of measured sodium exection) and the ability of the formula to discriminate sodium intake higher than 3.6 g/day was evaluated by ROC curve. Results: Correlation test between measured and estimated sodium was significant (r = 0.57; p < 0.001), but P30 test identified a low accuracy (61%) of the formula. Different cutoff points were tested by performance tests and a ROC curve was generated with the cutoff that showed better performance (3.6 g/day). An area under the curve of 0.69 with a sensitivity of 0.91 and specificity of 0.53 was obtained. Conclusion: A simple formula with high sensitivity in detecting patients with sodium consumption higher than 3.6 g/day from isolated urine sample was developed. Studies with a higher number of participants and with different populations are necessary to test formula´s validity.

Resumo Introdução: O consumo excessivo de sódio está relacionado a piores desfechos renais e cardiovasculares em pacientes com doença renal crônica (DRC), mas a avaliação deste consumo é complexa e mensurada com baixa frequência na prática clínica. Objetivo: Desenvolver uma nova fórmula para estimar a excreção de sódio de 24h a partir da concentração de sódio em amostra isolada da segunda urina do dia em pacientes com DRC pré-dialítica. Métodos: 51 participantes com DRC forneceram coleta de urina de 24h e uma amostra da segunda urina do dia para determinação da excreção de sódio. Uma fórmula para estimar a excreção de sódio de 24h foi desenvolvida a partir dos coeficientes da equação de regressão. A acurácia da fórmula foi testada por meio do cálculo do P30. A habilidade da fórmula em discriminar consumo de sódio superior a 3,6 g/dia foi avaliada pela curva ROC. Resultados: O teste de correlação entre sódio mensurado e estimado pela fórmula foi r = 0,57; p < 0,001, porém o resultado do P30 identificou baixa acurácia (61%). Diferentes pontos de corte foram testados por meio de testes de performance e uma curva ROC foi gerada com o ponto de corte de melhor performance (3,6 g/dia). Foi obtida uma área sob a curva de 0,69 com sensibilidade 0,91 e especificidade 0,53. Conclusão: Foi desenvolvida uma fórmula simples com elevada sensibilidade em detectar pacientes com consumo de sódio superior a 3,6 g/dia a partir de amostra de urina isolada. Estudos que testem a fórmula com um maior número de participantes e com outras populações são necessários.

Sodium and potassium intake estimated using two methods in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) / Consumo de sódio e potássio estimado por dois métodos no Estudo Longitudinal de Saúde do Adulto (ELSA-Brasil)

ABSTRACT CONTEXT AND OBJECTIVE: Sodium and potassium intake from different food sources is an important issue regarding cardiovascular physiology. Epidemiological assessment of the intake of these electrolytes intake is done through food frequency questionnaires or urinary excretion measurements. Our aim was to compare these methods using a sample of Brazilian civil servants. DESIGN AND SETTING: Cross-sectional baseline evaluation from the Brazilian Longitudinal Study of Adult Health. METHODS: Sodium and potassium intake was obtained using two methods: a semi-quantitative questionnaire including 114 food items; and overnight 12-hour urinary excretion measurement. Sodium and potassium estimates obtained through the questionnaire were adjusted for energy intake using the residual method. Urinary excretion measurements were considered valid if they met three adequacy criteria: collection time, volume and total creatinine excretion. Mean nutrients were estimated, and Spearman correlations were calculated. Sodium and potassium intake was categorized into quintiles, and weighted kappa coefficients and percentage agreement were calculated. The significance level for all tests was 0.05. RESULTS: Data from 15,105 participants were analyzed, and significant differences between mean intakes of sodium (questionnaire: 4.5 ± 1.7 g; urine: 4.2 ± 2.1 g) and potassium (questionnaire: 4.7 ± 1.8 g; urine: 2.4 ± 1 g) were found. Weak agreement was found for sodium (K = 0.18) and potassium (K = 0.16). The percentage disagreement between methods ranged from 41.8 to 44.5%, while exact concordance ranged from 22.1% to 23.9%. CONCLUSIONS: The agreement between the food frequency questionnaire and urinary excretion measurements for assessment of sodium and potassium intakes was modest.

RESUMO CONTEXTO E OBJETIVO: O consumo de sódio e potássio de diferentes fontes alimentares é uma questão importante para a fisiologia cardiovascular. A avaliação epidemiológica do consumo desses eletrólitos é feita pelo questionário de frequência alimentar ou pela excreção urinária. O objetivo deste estudo é comparar esses métodos em uma amostra de servidores públicos brasileiros. TIPO DE ESTUDO E LOCAL: Avaliação transversal da linha de base do Estudo Longitudinal de Saúde do Adulto. MÉTODOS: O consumo de sódio e potássio foi obtido por dois métodos: questionário semi-quantitativo com 114 itens alimentares e excreção urinária de 12 horas noturnas. Estimativas de sódio e potássio obtidas pelo questionário foram ajustadas pela energia utilizando o método residual. A excreção urinária foi considerada válida se atendesse a três critérios: tempo de coleta, volume e excreção total de creatinina adequados. Foram estimadas médias dos nutrientes e calculada a correlação de Spearman. O consumo de sódio e potássio foi categorizado em quintis e foram calculados o kappa ponderado e o percentual de concordância. O nível de significância para todos os testes foi de 0,05. RESULTADOS: Foram analisados dados de 15,105 participantes e encontradas diferenças significativas entre médias de sódio (questionário: 4,5 ± 1,7 g; urina: 4,2 ± 2,1 g) e potássio (questionário: 4,7 ± 1,8 g; urina: 2,4 ± 1 g). Foi encontrada fraca concordância para sódio (K = 0,18) e potássio (K = 0,16). Percentuais de discordância entre métodos variaram de 41,8-44,5%; concordâncias exatas de 22,1-23,9%. CONCLUSÃO: A concordância entre o questionário de frequência alimentar e excreção urinária para avaliação do consumo de sódio e potássio foi modesta.

Evaluación de la ingesta dietética y excreción urinaria de sodio y potasio en adultos / Assessment of dietary intake and urinary excretion of sodium and potassium in adults

Background: Hypertension is associated with elevated sodium and low potassium intakes. The determination of sodium and potassium intake by dietary records is inaccurate, being its measurement from 24-h urine collection the reference method. Aim: To determine urinary sodium and potassium excretion in adults. To compare dietary sodium and potassium intake and their excretion from an isolated urine sample against the reference method. Material and Methods: Seventy healthy adults aged 35 ± 8 years with a body mass index 25 ± 2 kg/m² (36 women) were studied. Urine was collected over 24 h, including an isolated urine sample taken in fasting conditions. Additionally, three 24-h dietary records were performed. Results: Reported sodium and potassium intake was 2,720 ± 567 and 1,068 ± 433 mg/day, respectively. In turn, urinary excretion of sodium and potassium was 4,770 ± 1,532 and 1,852 ± 559 mg/day, respectively. These latter values were significantly higher than those obtained by dietary records. Furthermore, the urinary sodium and potassium excretion estimated from an isolated urine sample was 4,839 ± 1,355 and 1,845 ± 494 mg/day, respectively. These values were similar to those obtained with a 24 h urine collection. Conclusions: Dietary records underestimated electrolyte intake when compared with the reference method. Using an isolated urine sample to estimate electrolyte intake may be a reliable alternative.

Estimating 24-Hour Urine Sodium Level with Spot Urine Sodium and Creatinine

The 24-hr urine sodium excretion level was estimated based on the spot urine sodium, and the efficacy of the formula was validated to determine the status of low salt intake or =100 mEq/day using the estimated amount> or =100 mEq/day was 84.3%, 87.6%, and 84.8%, respectively. In conclusion, the three equations used to estimate the 24-hr urine sodium content were useful to determine the status of low salt intake.

A Higher Salt Intake Leads to a Lower Rate of Adequate Blood Pressure Control

The relationship between salt intake and adequate blood pressure control is not well investigated in Korea populations, especially in patients with cardiovascular disease. This cross-sectional study enrolled 19,083 subjects who participated in the Korea National Health and Nutrition Examination Survey conducted from 2009-2011. The amount of salt intake was estimated using the Tanaka equations based on spot urine samples. Comparing patients with and without cardiovascular disease, systolic blood pressure (129.1+/-18.1 mmHg vs. 120.0+/-18.1 mmHg, P<0.001) and the amount of urinary sodium excretion (149.4+/-37.5 mM/day vs. 144.1+/-36.2 mM/day, P<0.001) were higher in patients with cardiovascular diseases. Among patients with cardiovascular disease, the high blood pressure group showed an increased amount of urinary sodium excretion compared to the normal blood pressure group (155.5+/-38.2 vs. 146.6+/-36.9 mM/day, P<0.001). The odds ratio (OR) of high blood pressure was higher (OR, 1.825; 95% CI, 1.187-2.807; P-for-trend 0.003, highest quartile of urinary sodium excretion vs. lowest quartile) in patients with cardiovascular disease. A higher amount of urinary sodium excretion was associated with a lower rate of adequate blood pressure control in Korean population, especially with cardiovascular disease.

Estimated 24-Hour Urine Sodium Excretion Is Correlated with Blood Pressure in Korean Population: 2009-2011 Korean National Health and Nutritional Examination Survey

No large-scale studies have investigated the association between salt intake and hypertension in Korean population. To investigate the relationship of blood pressure to salt consumption, we analyzed data from 19,476 participants in the 2009-2011 Korean National Health and Nutritional Examination Survey (KNHANES). Urinary sodium excretion over 24-hr (24HUNa) was estimated from spot urine tests using Tanaka's equation. The study subjects were stratified into hypertensive and normotensive groups. Hypertensive participants (n=6,552, 33.6%) had higher estimated 24HUNa, 150.4+/-38.8 mEq/day, than normotensive participants, 140.5+/-34.6 mEq/day (P<0.001). The association between 24HUNa and blood pressure outcomes was not affected by adjustment for other risk factors for hypertension (odds ratio 0.001; 95% confidence interval 0.001-0.003; P<0.001). Increases in 24HUNa of 100 mEq/day were associated with a 6.1+/-0.3/2.9+/-0.2 mmHg increase in systolic/diastolic blood pressure in all participants. This effect was stronger in hypertensive participants (increase of 8.1+/-0.5/3.4+/-0.3 mmHg per 100 mEq/day) and smaller in normotensive participants (2.9+/-0.3/1.3+/-0.2 mmHg). These results support recommendations for low salt intake in Korean population to prevent and control adverse blood pressure levels.

Analysis of Correlation between 24-Hour Urinary Sodium and the Degree of Blood Pressure Control in Patients with Chronic Kidney Disease and Non-Chronic Kidney Disease

We investigated the association between 24-hr urinary sodium (24UNA) and adequacy of blood pressure (BP) control in patients with chronic kidney disease (CKD) and nonCKD. All data were collected retrospectively by accessing the electrical medical records in patients with 24-hr urine collection and serum creatinine. Enrolled 400 subjects were subgrouped by the amount of 24UNA, or CKD stage. The appropriate BP was defined as BP or =90 mEq/day was 2.441 (1.249-4.772, P=0.009) higher than that of 24UNA <90 mEq/day among participants with proteinuria. There was difference in the amount of 24UNA between CKD and non-CKD except each stage of CKD group. In conclusion, salt intake estimated by 24-hr urine sodium excretion is a risk factor to achieve appropriate BP control.

Urinary Sodium Excretion Has Positive Correlation with Activation of Urinary Renin Angiotensin System and Reactive Oxygen Species in Hypertensive Chronic Kidney Disease

It is not well described the pathophysiology of renal injuries caused by a high salt intake in humans. The authors analyzed the relationship between the 24-hr urine sodium-to-creatinine ratio (24HUna/cr) and renal injury parameters such as urine angiotensinogen (uAGT/cr), monocyte chemoattractant peptide-1 (uMCP1/cr), and malondialdehyde-to-creatinine ratio (uMDA/cr) by using the data derived from 226 hypertensive chronic kidney disease patients. At baseline, the 24HUna/cr group or levels had a positive correlation with uAGT/cr and uMDA/cr adjusted for related factors (P or =200 mEq/g cr was higher than in patients with or =200 mEq/g cr (P=0.016). During the 16-week follow-up period, an increase in urinary sodium excretion predicted an increase in urinary angiotensinogen excretion. In conclusion, high salt intake increases renal renin-angiotensin-system (RAS) activation, primarily, and directly or indirectly affects the production of reactive oxygen species through renal RAS activation.

Estimated Amount of 24-Hour Urine Sodium Excretion Is Positively Correlated with Stomach and Breast Cancer Prevalence in Korea

Stomach cancer is one of the most common cancers in Korea. The aim of this study was to identify the association between the prevalence of cancer, particularly stomach cancer, and the amount of 24-hr urine sodium excretion estimated from spot urine specimens. The study included 19,083 subjects who took part in the Korean National Health and Nutritional Examination Survey between 2009 and 2011. The total amount of urine sodium excreted in a 24-hr period was estimated by using two equations based on the values for spot urine sodium and creatinine. In subjects who had an estimated 24-hr urine sodium excretion of more than two standard deviations above the mean (group 2), the prevalence of stomach cancer was higher than in subjects with lower 24-hr sodium excretion (group 1). By using the Tanaka equation to estimate it, the prevalence of stomach cancer was 0.6% (114/18,331) in group 1, whereas it was 1.6% (9/568) in group 2 (P=0.006). By using the Korean equation, the prevalence was 0.6% (115/18,392) in group 1, and 1.6% in group 2 (8/507) (P=0.010). By using the Tanaka equation, breast cancer in women is more prevalent in group 2 (1.9%, 6/324) than group 1 (0.8%, 78/9,985, P=0.039). Higher salt intake, as defined by the estimated amount of 24-hr urine sodium excretion, is positively correlated with a higher prevalence of stomach or breast cancer in the Korean population.