Egfr formula paediatrics
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eGFR formula paediatrics children estimated glomerular filtration rate
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Schwartz formula creatinine height children GFR calculation
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Here is a comprehensive overview of eGFR formulas used in paediatrics:
eGFR Formulas in Paediatrics
1. Modified Schwartz Formula (Preferred in Children)
This is the standard recommended formula for children (Management of Glomerular Diseases, p. 93).
$$\text{eGFR} = \frac{k \times \text{Height (cm)}}{\text{Serum Creatinine (mg/dL)}}$$
| Age Group | k constant |
|---|---|
| Infants (< 1 year, low birth weight) | 0.33 |
| Infants (< 1 year, term) | 0.45 |
| Children 1–12 years | 0.55 |
| Adolescent girls (13–21 yrs) | 0.55 |
| Adolescent boys (13–21 yrs) | 0.70 |
Units: eGFR in mL/min/1.73 m²
2. "Bedside" Modified Schwartz (2009) — Most Widely Used
The updated 2009 Schwartz formula uses a single k = 0.413 for all children aged 1–16 years, recalibrated for IDMS-traceable creatinine assays:
$$\text{eGFR} = \frac{0.413 \times \text{Height (cm)}}{\text{Serum Creatinine (mg/dL)}}$$
- This is the version used in most modern clinical and lab settings
- Requires only height and serum creatinine — simple bedside calculation
- Applicable from age 1 to 16 years
3. Full Age Spectrum (FAS) Equation
An alternative that spans both paediatric and adult populations seamlessly:
$$\text{eGFR} = \frac{107.3}{(\text{Creatinine} / Q)}$$
Where Q = median creatinine for age and sex (published reference values).
- Useful for transition-age adolescents (avoids the discontinuity between paediatric and adult equations)
- Validated across age groups from childhood through adulthood (Management of Glomerular Diseases, p. 93)
4. Cystatin C-Based Formulas (Children)
Used when creatinine generation is unreliable (e.g., low muscle mass, malnutrition, nephrotic syndrome with hypoalbuminemia):
Filler equation:
$$\text{eGFR} = 91.62 \times \left(\frac{1}{\text{Cystatin C}}\right)^{1.123}$$
Combined creatinine + cystatin C (Schwartz CKiD):
$$\text{eGFR} = 39.1 \times \left[\frac{\text{Height}}{\text{Creatinine}}\right]^{0.516} \times \left[\frac{1.8}{\text{Cystatin C}}\right]^{0.294} \times \left[\frac{30}{\text{BUN}}\right]^{0.169} \times \left[\frac{\text{Height}}{1.4}\right]^{0.188} \times [1.099]^{\text{male}}$$
Key Points
- Creatinine-based equations overestimate true GFR in nephrotic syndrome with hypoalbuminemia
- Cystatin C or combined equations are preferred when creatinine generation is disturbed
- In adolescents transitioning to adult care, the FAS equation avoids equation-switching discontinuity
- All paediatric eGFR formulas report in mL/min/1.73 m² (normalized to standard body surface area)
Sources: Management of Glomerular Diseases, p. 93 | Schwartz GJ et al., JASN 2009 | CKiD Study
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