Effect of indexed glomerular filtration rate according to age.

BACKGROUND

To find out up to what age there is dispersion in glomerular filtration rate (GFR) values when normalised by body surface area (BSA) and extracellular fluid volume (ECFV), based on the hypothesis that these values differ in childhood age.

METHODS

A retrospective study was performed on patients aged 0-85 years, with renal pathology, who were administered i.v. 51Cr-EDTA. GFR was obtained using the Ham and Piepsz (children) or Christensen and Groth (adults) formula. Results were normalised by BSA and ECFV.

RESULTS

The cut-off point is defined as the age that discriminates between values ± 10 points apart. Using a ROC curve analysis, this age was set at 11.96 years with a sensitivity of 0.83 and a specificity of 0.85. The area obtained was 0.902 (95%CI 0.880-0.923). The results were corroborated by linear regression stratifying by age. For children under 12 years of age, the Pearson correlation was 0.883 (95% CI 0.860-0.902). For those aged 12 years or older, this coefficient was 0.963 (95%CI 0.957-0.968). According to our results, when normalising GFR by BSA and by ECFV there are different behaviours according to age.

CONCLUSION

For children older than 12 years both normalisation methods can be used, but for children younger than 12 years there are differences. We believe that in children under 12 years of age, GFR should be normalised by ECFV.