Overnight urine collections to estimate sodium intake

Area of Science:

• Clinical Chemistry
• Nutritional Science
• Public Health

Background:

• Accurate assessment of sodium intake compliance is crucial for population health studies.
• Existing methods for measuring 24-hour urine sodium excretion can be cumbersome.
• Developing reliable, convenient methods for monitoring sodium balance is needed.

Purpose of the Study:

• To establish confidence limits for the relationship between nocturnal and 24-hour urine sodium excretion.
• To evaluate the utility of nocturnal urine chloride measurements for assessing sodium intake.
• To determine the accuracy of titrator sticks in estimating sodium excretion levels.

Main Methods:

• Collected urine samples from 24 men (12 white, 12 black) over 7 days at three sodium intake levels (10, 200, 400 mEq/day).
• Measured nocturnal and 24-hour urine sodium (Na) and chloride (Cl) excretion.
• Utilized titrator sticks for chloride measurements and performed discriminate analysis.

Main Results:

• Nocturnal urine Na and Cl showed high correlation (r ≥ 0.86, p < 0.001) with 24-hour urine sodium excretion (UNaV).
• Race did not significantly impact the observed relationships.
• Discriminate analysis achieved 85-95% accuracy in categorizing sodium intake levels using two nocturnal urine chloride measurements.
• Two nocturnal urine chloride measurements < 10 mEq accurately predicted 24-hour UNaV < 60 mEq (95% accuracy).

Conclusions:

• Nocturnal urine sodium and chloride excretion measurements are reliable indicators of 24-hour excretion.
• Titrator sticks provide a convenient, inexpensive, and accurate tool for assessing compliance with low sodium intake.
• These findings support the use of nocturnal urine analysis in population-based sodium compliance studies.