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Abstract: FR-PO565

Variability Between Measured Organic Acids and Net Acid Excretion and Estimated Organic Acids and Net Acid Production

Session Information

Category: Fluid‚ Electrolyte‚ and Acid-Base Disorders

  • 1002 Fluid‚ Electrolyte‚ and Acid-Base Disorders: Clinical

Authors

  • Banerjee, Tanushree, University of California San Francisco, San Francisco, California, United States
  • Frassetto, Lynda, University of California San Francisco, San Francisco, California, United States
Background

Formulas for diet acid load use estimates of organic acids (OA) production. Lemann et al. and Remer et al. have developed differing but widely used methods to estimate OA and hence net acid excretion (NAE) from diet composition. How well estimated dietary OA (DOA) correlates with measured urinary OA excretion (UOAE) is unclear, as is how much this variability contributes to variability in estimates of net endogenous acid production (NEAP) compared to measures of NAE.

Methods

24-hour urine from metabolic balance studies in 13 healthy males on a fixed diet/kg body weight were collected for 6 days sequentially at baseline and intervention phase. Measures for each time period were pooled. We compared repeated measures of UOAE to dietary OA estimates, and NAE to NEAP.
DOA was estimated from diet unmeasured anions by Lemann; Remer used individual body surface area (BSA). Lemann used urinary measurements of SO4 and OA to calculate NEAP, while Remer used BSA (using DuBois and Mosteller formulas) and dietary calculations of SO4. UOAE was measured by titration. We determined the concordance correlation coefficient (CCC) for the repeated measures data with the King et al. U-statistics approach (Stats Med 2007).

Results

13 males with a median age of 27 years were studied. The estimates of CCC and the confidence intervals are displayed below (Figure). CCC estimates indicate a very poor degree of agreement between UOAE and DOA using either Lemann’s or Remer’s methodology. We find a modest degree of agreement between NAE and NEAP with Lemann, and better concordance with Remer.

Conclusion

Dietary equations estimating OA production do not correlate well with the measured OA. This contributes to the variability for the dietary equations estimating NEAP. Using urinary citrate or targeted metabolomics in a clinical setting may be more accurate to quantify OA.