Low sodium status in cystic fibrosis-as assessed by calculating fractional Na+ excretion-is associated with decreased growth parameters

BackgroundIn CF infants, normonatremic Na+ depletion (NNaD), identified by fractional Na+ excretion (FENa) values < 0.5%, was recently linked to impaired growth. Our paper investigates the relationship between FENa and growth in CF children > 2 years.MethodsFENa values were calculated in 35 CF and 24 control children, and tested for correlations with z-scores for weight, height and BMI.ResultsAll CF children and controls had normal plasma Na+ concentrations. A total of 25 of 35 (71.4%) CF patients had decreased FENa values < 0.5% (group I). FENa results of 10 CF patients (group II) and 23/24 controls (group III) were normal. In Na+-depleted CF children, compared to normal controls, mean z-scores for weight (− 0.18 ± 0.87 vs + 1.03 ± 0.57, p < 0.001), height (− 0.06 ± 0.89 vs + 0.53 ± 0.72, p = 0.009) and BMI (− 0.22 ± 0.87 vs + 1.00 ± 1.06, p < 0.001) were significantly reduced. Also, we found positive correlations between FENa values and z-scores for weight (r = 0.521), height (r = 0.292) and BMI (r = 0.468), respectively.ConclusionNNaD may contribute to poor growth in CF.