Schwartz Bedside Paediatric eGFR Calculator
Schwartz Bedside Paediatric eGFR Calculator
Estimate GFR in children from height and creatinine using the bedside Schwartz equation.
Schwartz Bedside Paediatric eGFR
Paediatric equationHeight 120 cm, creatinine 0.6 mg/dL
Formula
- 0.413
- the bedside constant for IDMS-traceable enzymatic creatinine assays
- height
- cm — a proxy for muscle mass in children, which is why it replaces age and sex
- older constants
- 0.55, 0.45 and 0.7 appear in pre-2009 literature and apply to older, non-standardised assays
Worked example
Height 120 cm, creatinine 0.6 mg/dL
0.413 × 120 = 49.56
49.56 ÷ 0.6 = 83 mL/min/1.73 m²
Normal GFR by age
| Age | Approximate GFR (mL/min/1.73 m²) |
|---|---|
| 1 week (term) | 40 – 60 |
| 2 – 8 weeks | 60 – 80 |
| Over 8 weeks | 80 – 120 |
| 2 years to adult | 90 – 130 |
Using the bedside Schwartz equation
The bedside Schwartz equation replaces the age and sex terms of the adult equations with height, which in children is a better proxy for muscle mass and therefore for creatinine generation. It was revalidated in 2009 against iohexol-measured GFR in the CKiD cohort, and the constant of 0.413 belongs to that revalidation and to IDMS-traceable enzymatic creatinine assays.
Using an older constant is the commonest error. Values of 0.55 for children, 0.45 for infants and 0.7 for adolescent boys appear throughout the pre-2009 literature and were derived for Jaffe-based assays that read systematically higher. Applying them to a modern enzymatic creatinine overestimates GFR by roughly a third.
Two limits are worth stating. The equation was derived in children with chronic kidney disease and GFR between 15 and 75 mL/min/1.73 m², so it is least reliable in children with normal function. And normal GFR is age-dependent in a way that has no adult parallel: a healthy newborn has a GFR of 40 to 60 mL/min/1.73 m², rising to adult values by about two years. A result of 60 is severe impairment in a five-year-old and entirely normal in a two-week-old.
For children and young adults up to 25, the CKiD U25 equations are more accurate and are increasingly preferred.
Frequently asked questions
What is the bedside Schwartz equation?
eGFR equals 0.413 multiplied by height in centimetres divided by serum creatinine in mg/dL. It is the standard paediatric estimate for IDMS-traceable creatinine assays.
Why does the paediatric equation use height?
Height is a better proxy for muscle mass in a growing child than age or sex, and muscle mass determines creatinine generation.
Which constant should I use — 0.413 or 0.55?
0.413 for modern IDMS-traceable enzymatic assays. 0.55 and the other older constants were derived for Jaffe assays and overestimate GFR by about a third if used today.
What is a normal GFR in a baby?
Far lower than in an adult. A term newborn has a GFR of roughly 40 to 60 mL/min/1.73 m², reaching adult values by about two years of age.
Up to what age does Schwartz apply?
It is used through childhood and adolescence. From adolescence to age 25 the CKiD U25 equations are more accurate, and adult equations apply thereafter.
Related calculators
References
- Schwartz GJ et al. New equations to estimate GFR in children with CKD. J Am Soc Nephrol. 2009;20(3):629–37.
- KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease.