Estimation of 24-Hour Urinary Sodium Excretion Using Spot Urine Samples

• Published in: Nutrients Vol. 6; no. 6; pp. 2360 - 2375
• Main Authors: Rhee, Moo-Yong, Kim, Ji-Hyun, Shin, Sung-Joon, Gu, Namyi, Nah, Deuk-Young, Hong, Kyung-Soon, Cho, Eun-Joo, Sung, Ki-Chul
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 20.06.2014; MDPI
• Subjects: Adult; Blood pressure; Cardiology; Cholesterol; Clinical trials; Creatinine; equations; excretion; Female; Humans; Hypertension; Male; Medicine; Middle Aged; Nutrients; Reproducibility of Results; Sodium; Sodium - metabolism; Sodium - urine; Urine; Urine Specimen Collection - methods
• ISSN: 2072-6643; 2072-6643
• DOI: 10.3390/nu6062360

The present study evaluated the reliability of equations using spot urine (SU) samples in the estimation of 24-hour urine sodium excretion (24-HUNa). Equations estimating 24-HUNa from SU samples were derived from first-morning SU of 101 participants (52.4 ± 11.1 years, range 24–70 years). Equations developed by us and other investigators were validated with SU samples from a separate group of participants (n = 224, 51.0 ± 10.9 years, range 24–70 years). Linear, quadratic, and cubic equations were derived from first-morning SU samples because these samples had a sodium/creatinine ratio having the highest correlation coefficient for 24-HUNa/creatinine ratio (r = 0.728, p < 0.001). In the validation group, the estimated 24-HUNa showed significant correlations with measured 24-HUNa values. The estimated 24-HUNa by the linear, quadratic, and cubic equations developed from our study were not significantly different from measured 24-HUNa, while estimated 24-HUNa by previously developed equations were significantly different from measured 24-HUNa values. The limits of agreement between measured and estimated 24-HUNa by six equations exceeded 100 mmol/24-hour in the Bland-Altman analysis. All equations showed a tendency of under- or over-estimation of 24-HUNa, depending on the level of measured 24-HUNa. Estimation of 24-HUNa from single SU by equations as tested in the present study was found to be inadequate for the estimation of an individual’s 24-HUNa.