Estimating mean population salt intake in Fiji and Samoa using spot urine samples

Abstract

Background There is an increasing interest in finding less costly and burdensome alternatives to measuring population-level salt intake than 24-h urine collection, such as spot urine samples. However, little is known about their usefulness in developing countries like Fiji and Samoa. The purpose of this study was to evaluate the capacity of spot urine samples to estimate mean population salt intake in Fiji and Samoa. Methods The study involved secondary analyses of urine data from cross-sectional surveys conducted in Fiji and Samoa between 2012 and 2016. Mean salt intake was estimated from spot urine samples using six equations, and compared with the measured salt intake from 24-h urine samples. Differences and agreement between the two methods were examined through paired samples t-test, intraclass correlation coefficient analysis, and Bland-Altman plots and analyses. Results A total of 414 participants from Fiji and 725 participants from Samoa were included. Unweighted mean salt intake based on 24-h urine collection was 10.58 g/day (95% CI 9.95 to 11.22) in Fiji and 7.09 g/day (95% CI 6.83 to 7.36) in Samoa. In both samples, the INTERSALT equation with potassium produced the closest salt intake estimate to the 24-h urine (difference of − 0.92 g/day, 95% CI − 1.67 to − 0.18 in the Fiji sample and + 1.53 g/day, 95% CI 1.28 to 1.77 in the Samoa sample). The presence of proportional bias was evident for all equations except for the Kawasaki equation. Conclusion These data suggest that additional studies where both 24-h urine and spot urine samples are collected are needed to further assess whether methods based on spot urine samples can be confidently used to estimate mean population salt intake in Fiji and Samoa.

Further evidence that methods based on spot urine samples should not be used to examine sodium‐disease relationships from the Science of Salt: A regularly updated systematic review of salt and health outcomes (November 2018 to August 2019)

“…He and colleagues report further evidence that estimates of sodium intake from methods based on spot urine samples are inaccurate and biased by systematic error, 23 which is consistent with previous findings in diverse populations 56‐60 . Furthermore, for the first time, He et al 23 provide novel data suggesting that the use of the Kawasaki equation, a spot urine‐based estimate, changes the linearity of the sodium‐mortality association.…”

A method to monitor the national salt reduction efforts in Sri Lanka and status of salt, potassium and iodine intake in an adult Sri Lankan community

“…There has been much interest in using spot urine (SU) sodium measurements as a replacement for 24-hU collection (PAHO, 2010). There are several equations which have been tested in many countries to calculate salt intake from SU samples (Kawasaki et al, 1993;Tanaka et al, 2002;Mage et al, 2008;Brown et al, 2013;Whitton et al, 2016;Santos et al, 2019;Xu et al, 2020), but these equations have not been evaluated in the Sri Lankan population.…”

“…To maintain the accuracy of 24-hU samples, the following samples were excluded from the final analysis based on the following established criteria; total urine volume was < 500 mL or total creatinine excretion of women was < 4 mmol/day or > 25 mmol/day, and men was < 6 mmol/day or > 30 mmol/day. In addition, spot urine samples were excluded based on the following criteria: creatinine concertation was < 1.8 mmol/L for both sexes, or > 28.3 mmol/L for women and > 32.7 mg/L for men (Santos et al, 2019). 24hUNa and potassium concentrations (mmol/L) were multiplied by the urine volume (L), to obtain 24-hUNa and potassium excretion (mmol/day).…”

Change in mean salt intake over time using 24-h urine versus overnight and spot urine samples: a systematic review and meta-analysis

“…All data generated or analysed during this study are included within the article and additional files. The contents of this manuscript are based on a Master's thesis (2017) submitted to the School of Public Health, Faculty of Medicine, The University of Sydney [34].…”

“…The contents of this manuscript are based on a Master’s thesis (2017) submitted to the School of Public Health, Faculty of Medicine, The University of Sydney [ 34 ].…”