Correlation of 24-Hour Urine Sodium, Potassium and Calcium Measurements with Spot Urine

Relationship between urinary sodium-creatinine ratios and insulin resistance in Korean children and adolescents with obesity

BACKGROUND

The prevalence of childhood obesity has significantly increased in Korea. This study aimed to use data from the 2010 Korea National Health and Nutrition Examination Survey (KNHANES) to investigate the association between sodium (Na) intake and insulin resistance in children and adolescents with obesity.

METHODS

The study population consisted of 578 adolescents aged 12-18 years who were enrolled in the 2010 KNHANES. Subjects were classified into the following four groups based on their body mass index (BMI) and homeostatic model assessment-insulin resistance (HOMA-IR) values: normal BMI and HOMA-IR (Group 1), normal BMI and ≥75% HOMA-IR (Group 2), ≥85% BMI and normal HOMA-IR (Group 3) and ≥85% BMI and ≥75% HOMA-IR (Group 4). The groups were further divided into four quartiles (Q1-Q4) based on urinary sodium-creatinine ratios (UNa/Cr) to analyze the association between obesity and metabolic abnormality as a result of increased Na intake.

RESULTS

There were significant differences among the four groups in terms of abdominal obesity (p<0.000), waist circumference (WC) (p<0.000) blood glucose levels (p<0.000), insulin levels (p<0.000) and UNa/Cr, with Groups 2, 3 and 4 having significantly higher UNa/Cr than Group 1 (p=0.002). In addition, there was a significant positive correlation between UNa/Cr and obesity (Q1=1 vs. Q4=3.23, p=0.019) and metabolic abnormality (Q1=1 vs. Q4=2.25, p=0.167).

CONCLUSIONS

Increased Na intake showed a positive statistical correlation with insulin resistance and is associated with an increased risk of insulin resistance and other metabolic abnormalities in obese children and adolescents.

Reliable Quantification of the Potential for Equations Based on Spot Urine Samples to Estimate Population Salt Intake: Protocol for a Systematic Review and Meta-Analysis

Background

Methods based on spot urine samples (a single sample at one time-point) have been identified as a possible alternative approach to 24-hour urine samples for determining mean population salt intake.

Objective

The aim of this study is to identify a reliable method for estimating mean population salt intake from spot urine samples. This will be done by comparing the performance of existing equations against one other and against estimates derived from 24-hour urine samples. The effects of factors such as ethnicity, sex, age, body mass index, antihypertensive drug use, health status, and timing of spot urine collection will be explored. The capacity of spot urine samples to measure change in salt intake over time will also be determined. Finally, we aim to develop a novel equation (or equations) that performs better than existing equations to estimate mean population salt intake.

Methods

A systematic review and meta-analysis of individual participant data will be conducted. A search has been conducted to identify human studies that report salt (or sodium) excretion based upon 24-hour urine samples and spot urine samples. There were no restrictions on language, study sample size, or characteristics of the study population. MEDLINE via OvidSP (1946-present), Premedline via OvidSP, EMBASE, Global Health via OvidSP (1910-present), and the Cochrane Library were searched, and two reviewers identified eligible studies. The authors of these studies will be invited to contribute data according to a standard format. Individual participant records will be compiled and a series of analyses will be completed to: (1) compare existing equations for estimating 24-hour salt intake from spot urine samples with 24-hour urine samples, and assess the degree of bias according to key demographic and clinical characteristics; (2) assess the reliability of using spot urine samples to measure population changes in salt intake overtime; and (3) develop a novel equation that performs better than existing equations to estimate mean population salt intake.

Results

The search strategy identified 538 records; 100 records were obtained for review in full text and 73 have been confirmed as eligible. In addition, 68 abstracts were identified, some of which may contain data eligible for inclusion. Individual participant data will be requested from the authors of eligible studies.

Conclusions

Many equations for estimating salt intake from spot urine samples have been developed and validated, although most have been studied in very specific settings. This meta-analysis of individual participant data will enable a much broader understanding of the capacity for spot urine samples to estimate population salt intake.