Estimating mean population salt intake using spot urine samples in Nepal: a cross-sectional study

Area of Science:

• Public Health
• Nutritional Epidemiology
• Urology

Background:

• Estimating population salt intake is crucial for public health initiatives, particularly in low-income settings where 24-hour urine collection is challenging.
• Spot urine testing offers a potentially more practical alternative to 24-hour urine samples for large-scale surveys.
• The accuracy of existing spot urine-based equations for estimating salt intake in diverse populations, such as Nepal, remains under-investigated.

Purpose of the Study:

• To compare salt intake estimates derived from spot urine samples using established equations against 24-hour urine samples in a Nepalese population.
• To evaluate the predictive accuracy of various spot urine-based equations for estimating 24-hour salt intake.
• To explore the utility of spot urine samples for predicting 24-hour creatinine and potassium excretion.

Main Methods:

• Utilized data from a 2018 community-based survey in Nepal, including 451 participants with both 24-hour and spot urine samples.
• Estimated mean salt intake from spot urine using multiple previously published prediction equations.
• Compared spot urine-derived estimates with 24-hour urine collection measurements using statistical analyses (paired t-test, correlation, Bland-Altman plots).

Main Results:

• The mean salt intake from 24-hour urine samples was 13.28 ± 4.72 g/day.
• All evaluated spot urine-based equations demonstrated significant mean differences (biases) when compared to 24-hour urine estimates.
• The Uechi regression equation exhibited the smallest bias, with a 9% underestimation (-1.21 g/day), but proportional biases were observed across all equations.

Conclusions:

• Existing spot urine-based equations do not accurately reflect 24-hour salt intake in the Nepalese population studied.
• While potentially useful for longitudinal monitoring, current equations have limitations for precise mean salt intake estimation in Nepal.
• Further research is warranted to develop and validate accurate spot urine-based methods for salt intake assessment in this population.