Evaluation of Failure to Thrive: Diagnostic Yield of Testing for Renal Tubular Acidosis

RTA is a rare renal cause of FTT in children. VBG determination of serum bicarbonate yielded a significantly higher value than the result obtained by routine biochemical testing under both in vitro and in vivo conditions. These data suggest that reliance on routine biochemical testing results in an overestimation of the importance of RTA as a cause of FTT. We recommend the use of a VBG determination of serum bicarbonate concentration for the evaluation of a child with FTT who is thought to have a metabolic acidosis. Adoption of this practice will reduce the number of children suspected of having RTA and decrease the need for referral to a nephrologist for further evaluation.