New equations to estimate GFR in children with CKD

J Am Soc Nephrol. 2009 Mar;20(3):629-37. doi: 10.1681/ASN.2008030287. Epub 2009 Jan 21.

Abstract

The Schwartz formula was devised in the mid-1970s to estimate GFR in children. Recent data suggest that this formula currently overestimates GFR as measured by plasma disappearance of iohexol, likely a result of a change in methods used to measure creatinine. Here, we developed equations to estimate GFR using data from the baseline visits of 349 children (aged 1 to 16 yr) in the Chronic Kidney Disease in Children (CKiD) cohort. Median iohexol-GFR (iGFR) was 41.3 ml/min per 1.73 m(2) (interquartile range 32.0 to 51.7), and median serum creatinine was 1.3 mg/dl. We performed linear regression analyses assessing precision, goodness of fit, and accuracy to develop improvements in the GFR estimating formula, which was based on height, serum creatinine, cystatin C, blood urea nitrogen, and gender. The best equation was: GFR(ml/min per 1.73 m(2))=39.1[height (m)/Scr (mg/dl)](0.516) x [1.8/cystatin C (mg/L)](0.294)[30/BUN (mg/dl)](0.169)[1.099](male)[height (m)/1.4](0.188). This formula yielded 87.7% of estimated GFR within 30% of the iGFR, and 45.6% within 10%. In a test set of 168 CKiD patients at 1 yr of follow-up, this formula compared favorably with previously published estimating equations for children. Furthermore, with height measured in cm, a bedside calculation of 0.413*(height/serum creatinine), provides a good approximation to the estimated GFR formula. Additional studies of children with higher GFR are needed to validate these formulas for use in screening all children for CKD.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adolescent
  • Biometry
  • Blood Urea Nitrogen
  • Body Height
  • Child
  • Child, Preschool
  • Cohort Studies
  • Contrast Media / pharmacokinetics
  • Creatinine / blood
  • Cystatin C / blood
  • Female
  • Glomerular Filtration Rate*
  • Humans
  • Infant
  • Iohexol / pharmacokinetics
  • Linear Models
  • Male
  • Models, Biological
  • Renal Insufficiency, Chronic / blood
  • Renal Insufficiency, Chronic / pathology
  • Renal Insufficiency, Chronic / physiopathology*
  • Sex Characteristics

Substances

  • Contrast Media
  • Cystatin C
  • Iohexol
  • Creatinine