Performance of Predictive Equations and Biochemical Measures Quantifying Net Endogenous Acid Production and the Potential Renal Acid Load.

INTRODUCTION

A limited number of studies have assessed the accuracy and precision of methods for determining the net endogenous acid production (NEAP) and its components. We aimed to investigate the performance of methods quantifying the diet dependent acid-base load.

METHODS

Data from metabolic balance studies enabled calculations of NEAP according to the biochemical measures (of net acid excretion [NAE], urinary net endogenous acid production [NEAP], and urinary potential renal acid load [PRAL]) as well as estimative diet equations (by Frassetto , Remer and Manz, Sebastian , and Lemann) that were compared among themselves in healthy participants fed both acid and base forming diets for 6 days each.

RESULTS

Seventeen participants (mean ± SD age, 60 ± 8 years; body mass index, 23 ± 2 kg/m) provided 102 twenty-four-hour urine samples for analysis (NAE, 39 ± 38 mEq/d [range, -9 to 95 mEq/d]). Bland-Altman analysis comparing NEAP to NAE showed good accuracy (bias, -2 mEq/d [95% confidence interval {CI}, -8 to 3]) and modest precision (limits of agreement, -32 to 28 mEq/d). Accurate diet equations included potential renal acid load (PRAL) by Sebastian (bias, -4 mEq/d [95% CI, -8 to 0]) as well as NEAP by Lemann (bias, 4 mEq/d [95% CI, -1 to 9]) and Remer and Manz (bias, -1 mEq/d [95% CI, -6 to 3]).

CONCLUSIONS

Researchers are encouraged to collect measures of PRAL and NEAP; however, investigators drawing conclusions between the diet-dependent acid-base load and human health should consider the limitations within all methods.