PS-C35-1: SPOT URINE SODIUM: CREATININE RATIO: A SIMPLE METHOD TO ESTIMATE SODIUM INTAKE

Abstract

Objective: High sodium intake is a worldwide problem and contributes to high blood pressure and target organ damage. Measurement of 24-hour urine sodium excretion is gold standard for sodium intake evaluation but it is difficult to practice. In this study, the correlation between spot urine sodium: creatinine ratio from second void (AM), before dinner (PM), before bedtime (HS) and 24-hr samples with 24-hour urine sodium were evaluated. Methods: The participants were recruited from single hospital. Participants with age > 20 years, eGFR > 60 ml/min/1.73 m2 and no history of diuretics use were included. Urine sodium, urine creatinine and urine volume of each sample were measured. Urine sodium (mmol/L): urine creatinine (mg/dL) ratio of AM, PM, HS and 24-hour samples were calculated. Correlations of each ratio with 24 hour urine sodium (mmol/day) were studied by Pearson correlation coefficients. Results: 43 participants were included in this study. Mean age was 46.9 ± 13.6 years. Hypertension was diagnosed in 31 participants (72%). Mean blood pressure was 134 ± 15/81 ± 9 mmHg. Estimated eGFR was 100 ± 16 ml/min/1.73 m2. Mean 24 hour urine sodium was 178 + 92 mmol/day (equivalent to sodium intake 4,094 + 2,116 mg/day). Urine sodium: creatinine ratio of AM, PM, HS and 24-hr samples (correlation coefficient, r, with 24-hour urine sodium excretion) were 1.6 ± 0.8 (r = 0.11, P = 0.49), 1.9 ± 1.1 (r = 0.71, P < 0.001), 1.7 ± 1.1 (r = 0.59, P < 0.001) and 1.8 ± 0.7 (r = 0.77, < 0.001) respectively. Spot urine sodium: creatinine ratio from PM sample cut-off point of 1.2 had sensitivity of 81% and specificity of 73% to determine 24-hr urine sodium of 100 mmol/day. Conclusions: Spot urine sodium: creatinine ratio from PM sample correlates well with 24-hr urine sodium (r = 0.62) and ratio of 1.2 is equivalent to 24-hr urine sodium of 100 mmol/day. Sodium intake of study participants was 178 mmol/day which higher than recommended level.