Can spot urine measurement be a substitute for 24-hour urine measurement to estimate sodium intake in adolescents?

Importance:Several methods have been established in recent decades that allow use of spot urine to estimate dietary sodium intake.However,their accuracies have been controversial in children.Objective:To validate the performance of three commonly used methods-the Kawasaki,Tanaka,and International Cooperative Study on Salt,Other Factors,and Blood Pressure(INTERSALT)methods.Additionally,this study explored the accuracies of the Tanaka and INTERSALT methods by using spot urine samples taken at four separate times.Method:Forty-one adolescents aged 14 to 16 years completed two non-consecutive 24-hour urine collections and their mean values were used as reference data.The second-morning urine was used for assessment with the Kawasaki method;a casual spot urine and spot urine samples taken at four separate times(morning,afternoon,evening,and overnight)were used for assessment with the Tanaka and INTERSALT methods.Results:The mean differences were 1801 mg,542 mg,47 mg,and-31 mg for the Kawasaki,Tanaka,INTERSALT 1(with potassium),and INTERSALT2(without potassium)methods with their required spot urine,respectively.The proportions of relative difference levels within±10%were 4.9%for the Kawasaki method,19.5%for the Tanaka method,36.6%for the INTERSALT 1 method,and 36.6%for the INTERSALT2 method.Interpretation:The INTERSALT method seemed to provide minimally biased estimations of mean population sodium intake with casual spot urine.However,there is a need to be cautious regarding inconsistencies in estimation among different levels of sodium intake.The methods assessed in this study were unable to accurately estimate sodium intake at the individual level.

Cosinor-rhythmometry for 24-h urinary sodium,potassium,creatinine excretion in the Chinese adult population

Background:The low accuracy of equations predicting 24-h urinary sodium excretion using a single spot urine sample contributed to the misclassification of individual sodium intake levels.The application of single spot urine sample is limited by a lack of representativity of urinary sodium excretion,possibly due to the circadian rhythm in urinary excretion.This study aimed to explore the circadian rhythm,characteristics,and parameters in a healthy young adult Chinese population as a theoretical foundation for developing new approaches.Methods:Eighty-five participants(mean age 32.4 years)completed the 24-h urine ollction by sccessively cllecing each of the single-voided specimens within 24 h.The concentrations of the urinary sodium,potassium,and creatinine for cach voided specimen were measured.Cosinor analysis was applied to explore the circadian rhythm of the urinary sodium,potassium,and creatinine excretion.The excretion per hour was computed for analyzing the change over time with repeated-measures analysis of variance and a cubic spline model.Results:The metabolism of urinary sodium,potassium,and creatinine showed different patterns of circadian rhythm,although the urinary sodiurm excretion showed non-significant parameters in the cosinor model.A significant circadian rhythm of urinary creatinine excretion was observed,while the circadian rhythm of sodium was less significant than that of potassium.The circadian rhythm of urinary sodium and creatinine excretion showed synchronization to some extent,which had a nocturnal peak and fell to the lowest around noon to afternoon.In contrast,the peak of potassium was observed in the morning and dropped to the lowest point in the evening.The hourly urinary excretion followed a similar circadian rhythm.Conclusion:It is necessary to consider the circadian rhythm of urinary sodium,potassium,and creatinine excretion in adults while exploring the estimation model for 24-h urinary sodium excretion using spot urine.