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Abstract: PO1502

Multiple Spot Urine Sampling Is More Precise and Accurate Than 24-Hour Urine Collection for Estimating Urinary Sodium Excretion

Session Information

Category: Fluid, Electrolyte, and Acid-Base Disorders

  • 901 Fluid, Electrolyte, and Acid-Base Disorders: Basic

Authors

  • Ardissino, Gianluigi, Pediatric Nephrology, Dialysis and Transplantation, Fondazione IRCCS Ca’ Granda, Ospedale Maggiore Policlinico, Milano, Italy
  • Vergori, Antonio, Pediatric Nephrology, Dialysis and Transplantation, Fondazione IRCCS Ca’ Granda, Ospedale Maggiore Policlinico, Milano, Italy
  • Vergori, Cesare, Pediatric Nephrology, Dialysis and Transplantation, Fondazione IRCCS Ca’ Granda, Ospedale Maggiore Policlinico, Milano, Italy
  • Martelli, Laura, Pediatric Nephrology, Dialysis and Transplantation, Fondazione IRCCS Ca’ Granda, Ospedale Maggiore Policlinico, Milano, Italy
  • Ghiglia, Silvia A.C, Cardiology Unit, Fondazione IRCCS Ca’ Granda, Ospedale Maggiore Policlinico, Milano, Italy
  • Giussani, Antenore, Renal Transplant Unit, Fondazione IRCCS Ca’ Granda, Ospedale Maggiore Policlinico, Milano, Italy
  • Monzani, Alice, Dept. of Pediatrics, Novara, Italy
  • Pieri, Giovanni Raimondo, Pediatric Nephrology, Dialysis and Transplantation, Fondazione IRCCS Ca’ Granda, Ospedale Maggiore Policlinico, Milano, Italy
  • Brambilla, Marta, Pediatric Nephrology, Dialysis and Transplantation, Fondazione IRCCS Ca’ Granda, Ospedale Maggiore Policlinico, Milano, Italy
  • Salice, Patrizia, Cardiology Unit, Fondazione IRCCS Ca’ Granda, Ospedale Maggiore Policlinico, Milano, Italy
  • Bosco, Annalisa, Pediatric Nephrology, Dialysis and Transplantation, Fondazione IRCCS Ca’ Granda, Ospedale Maggiore Policlinico, Milano, Italy
  • Mancuso, Maria Cristina, Pediatric Nephrology, Dialysis and Transplantation, Fondazione IRCCS Ca’ Granda, Ospedale Maggiore Policlinico, Milano, Italy
  • Marsciani, Martino, UO Pediatria e Terapia Intensiva Pediatrica-Neonatale - Ospedale Bufalini, Cesena, Italy
  • Romano, Roberto, Pediatric Nephrology, Dialysis and Transplantation, Fondazione IRCCS Ca’ Granda, Ospedale Maggiore Policlinico, Milano, Italy
  • Perrone, Michela, Pediatric Nephrology, Dialysis and Transplantation, Fondazione IRCCS Ca’ Granda, Ospedale Maggiore Policlinico, Milano, Italy
  • Capone, Valentina, Pediatric Nephrology, Dialysis and Transplantation, Fondazione IRCCS Ca’ Granda, Ospedale Maggiore Policlinico, Milano, Italy
Background

The estimate of sodium excretion (NaE) is important for the management of hypertension, but 24 hours urinary collection (24-hrsUC), the current standard of care, can be inaccurate, unpractical and poorly representative of the usual Na intake. Multiple spot urine sampling is not affected by any of these errors, so we hypotesized that it can be equally or more precise than 24-hrsUC for estimating NaE.

Methods

4/subject 24-hrsUC and the related 439 urine samples (1/voiding), were analyzed for uNa and uCr. uNaE (in mEq/Kg/day) of each 24-hrsUC and uNa/uCrR of each voiding were calculated. Individual uNa excretion from 24-hrsUC were compared with all the means of uNa/uCrR derived from 2, 3 and 4 random samples from different days for both precision and accuracy using the mean of all the 24-hrsUC as individual “gold standard”. Precision in estimating the gold standard of the 2 methods was measured by comparing the respective coefficient of variations (CV). Accuracy was measured by comparing the P30 and P20 of the 2 methods after transforming uNa/uCrR into uNaE in (mEq/kg/day) by means of the equations (one for children and one for adults) derived from the study data set.

Results

CV of 24-hrs-UCs was 25.7% and that of uNa-to-uCrR as derived from the mean of 2, 3 and 4 samples were respectively 37.1, 28.2 and 22.5%. The CVs were significantly higher in children. Accuracy: P30 and P20 of the 24-hrs-UC were 62.5% and 78.7%, respectively. The corresponding figures obtained from all the 20,258 possible means of 4 samples randomly taken from different days were 73.1% and 94.5%. The internal validation performed by the same subjects 1 year after and the external validation in 8 subjects confirmed the superiority of multiple spot urine sampling.

Conclusion

In real life, with various sources of error systematically affecting 24-hrs-UCs, uNa-to-uCrR will have an even higher precision and accuracy and should be preferred for estimating uNaE.