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Determination of a new constant to estimate glomerular filtration rate in pediatrics

Melina Porporato1, Elsa Isern1, Mariana Pellegrini1

  • 1Sección Nefrología Infantil, Hospital Profesor Alejandro Posadas, Buenos Aires, Argentina.

Archivos Argentinos De Pediatria
|September 27, 2021
PubMed

Insights

This study determined a new constant (k=0.499) for estimating glomerular filtration rate (GFR) in pediatric patients using the compensated kinetic colorimetric assay (CKC) for plasma creatinine measurement. This improves GFR estimation accuracy in children.

Area of Science:

  • Pediatric Nephrology
  • Clinical Chemistry

Background:

  • Glomerular filtration rate (GFR) estimation in pediatrics commonly uses formulas like the Schwartz formula, relying on plasma creatinine levels.
  • The accuracy of these formulas depends on the constant 'k,' which varies with the plasma creatinine assay method.
  • Existing 'k' values may not be accurate for newer methods like the compensated kinetic colorimetric assay (CKC).

Purpose of the Study:

  • To determine an accurate constant 'k' for the Schwartz formula when using the CKC method for plasma creatinine measurement in pediatric patients.
  • To improve the reliability of estimated GFR (eGFR) in children.

Main Methods:

  • A correlational, descriptive study design was employed.
  • 184 pediatric patients (aged 3-18 years) with normal or altered GFR were included.
  • Plasma and urine creatinine, height, and 24-hour urine output were measured.

Main Results:

  • A new constant 'k' of 0.499 was calculated based on linear correlation between height, plasma creatinine, and measured corrected creatinine clearance (mcCrCl).
  • The correlation coefficient (r) was 0.974 and r-squared (r2) was 0.949 for the height/creatinine/mcCrCl relationship.
  • The correlation between eGFR using the new 'k' value and mcCrCl showed a high coefficient (ß = 0.999, r = 0.951, r2 = 0.903).

Conclusions:

  • The calculated constant k = 0.499 is suitable for estimating GFR in pediatric patients when plasma creatinine is measured using the CKC method.
  • This finding enhances the accuracy of GFR estimation in children, aiding in diagnosis and management of kidney conditions.
Abstract

Keywords:
colorimetric assaycreatinineglomerular filtration rate

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