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Estimating 24-Hour Urine Sodium From Multiple Spot Urine Samples
Moo-Yong Rhee1,2, Ji-Hyun Kim1, Sung-Joon Shin3
1Cardiovascular Center, Dongguk University Ilsan Hospital, Goyang-si, Gyeonggi-do, Korea.
Journal of Clinical Hypertension (Greenwich, Conn.)
|October 14, 2016
Summary
Estimating 24-hour urine sodium (24HUNa) is improved by averaging three spot urine (SU) samples. This new equation offers lower bias and better accuracy for population-level sodium assessment compared to single SU sample methods.
Area of Science:
- Clinical Chemistry
- Biomarker Validation
- Urine Analysis
Background:
- Accurate 24-hour urine sodium (24HUNa) excretion is crucial for cardiovascular health management.
- Traditional 24-hour urine collection is cumbersome, leading to interest in spot urine (SU) estimations.
- Existing SU-based equations for 24HUNa estimation exhibit significant bias and variability.
Purpose of the Study:
- To develop and validate a novel equation for estimating 24-hour urine sodium (24HUNa) using multiple spot urine (SU) samples.
- To compare the accuracy and reliability of the new multi-SU equation against existing single-SU equations.
Main Methods:
- Developed an equation using the average of three spot urine (SU) samples (morning-first, morning, evening) from 74 individuals.
- Validated the equation using three SU samples (morning-first, daytime, evening) from 174 additional individuals.
- Assessed bias, intraclass correlation, concordance correlation, and limits of agreement against measured 24HUNa.
Main Results:
- The developed equation using three SU samples demonstrated significantly lower bias (-2.9 mmol/24 h) compared to previous single-SU equations (>10 mmol/24 h).
- Intraclass and concordance correlation coefficients were high (0.909 and 0.832, respectively), indicating good reliability.
- The limits of agreement were narrower for the new equation (-64.1–58.3 mmol/24 h) than for previous methods (approx. 100 mmol/24 h).
Conclusions:
- An equation utilizing the average of three spot urine samples provides a more accurate and less biased estimation of 24-hour urine sodium excretion at a population level.
- This multi-sample SU approach offers a practical alternative to timed 24-hour urine collections for sodium assessment.
- Further research may refine multi-SU equations for improved individual 24HUNa estimation.
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