Bedside Schwartz

Bedside creatinine and height equation for children with CKD

Biomarkers
Creatinine
Validated for
1–16 years
Inputs
Age, Height, Creatinine
Reports
mL/min/1.73 m²
Published
2009

The eGFR guide explains which equation the calculator suggests and indexed and absolute GFR.

Formula

eGFR=41.3×heightScr (height in meters)\text{eGFR} = 41.3 \times \frac{\text{height}}{S_{cr}} \text{ (height in meters)}

As text: eGFR = 41.3 × height / Scr (height in meters)

Constants

SymbolMeaningValue
41.3Bedside coefficient (CKiD 2009, enzymatic creatinine)
HeightPatient height (input)meters
ScrS_{cr}Serum creatinine (IDMS-standardized) (input)mg/dL

How it was developed

Developed in 349 children aged 1 to 16 years with mild to moderate CKD in the North American Chronic Kidney Disease in Children (CKiD) cohort, with GFR measured by plasma iohexol disappearance. The 41.3 coefficient comes from a regression on height over enzymatic serum creatinine with the exponent fixed at 1.

Clinical notes

  • Bedside approximation of the full 2009 CKiD equation with cystatin C and BUN
  • Built on enzymatic creatinine that agreed with an IDMS-traceable method
  • Updates the original Schwartz k of 0.55, derived with Jaffe creatinine

Limitations

  • Not developed in infants under 1 year or adolescents over 16
  • Stated for GFR 15–75 mL/min/1.73 m²; not tested at higher GFR
  • Cohort had growth retardation and delayed puberty

References

  1. Schwartz GJ, Muñoz A, Schneider MF, et al. New equations to estimate GFR in children with CKD. J Am Soc Nephrol. 2009;20(3):629-637. doi:10.1681/ASN.2008030287

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