Is a Serum Creatinine of 0.45 mg/dL Normal in an 11-Year-Old Child?
A serum creatinine of 0.45 mg/dL is within the normal range for an 11-year-old child and does not indicate kidney dysfunction.
Normal Pediatric Creatinine Values
- Normal serum creatinine in children varies by age, sex, and muscle mass, with values typically lower than adults due to smaller muscle mass 1, 2.
- Reference intervals for children show that creatinine values progressively increase with age as muscle mass develops 3.
- The revised Bedside Schwartz equation should be used to estimate GFR rather than relying on creatinine alone, as serum creatinine concentration is influenced by muscle mass, age, gender, and tubular secretion 4.
Calculating Estimated GFR
Using the revised Bedside Schwartz equation for enzymatic creatinine assays:
eGFR = 0.413 × [height (cm) / serum creatinine (mg/dL)] 4
For an 11-year-old with creatinine 0.45 mg/dL:
- Assuming average height of approximately 145 cm for an 11-year-old
- eGFR = 0.413 × (145 / 0.45) = 133 mL/min/1.73 m²
This is well above the normal pediatric GFR range of 100–120 mL/min/1.73 m², indicating excellent kidney function 4.
Clinical Interpretation
- An eGFR < 90 mL/min/1.73 m² should be flagged as "low" in children over age 2 years, but this child's estimated GFR exceeds this threshold by a substantial margin 5.
- Normal GFR for children older than 2 years is approximately 100–120 mL/min/1.73 m² after body surface area adjustment 4.
- Serum creatinine should never be used in isolation to assess renal function in children because its concentration is influenced by multiple non-renal factors 4.
Important Caveats
- Ensure the laboratory used an enzymatic creatinine assay, as the Jaffe method can overestimate creatinine in children due to non-creatinine chromogens, particularly in neonates with icteric or hemolyzed samples 5.
- The assay should have a coefficient of variation < 2.3% for creatinine with calibration traceable to international standard reference materials 5.
- Dietary creatine intake can artificially elevate serum creatinine—homemade formulas or supplements containing beef liver or creatine powders can cause spurious elevations that normalize within 12 hours of discontinuation 6.
When to Investigate Further
- If eGFR is calculated to be < 90 mL/min/1.73 m², repeat the measurement and consider confirming with cystatin C-based estimation 4.
- A cystatin C concentration of ≥ 1.06 mg/L predicts a GFR < 80 mL/min/1.73 m² with 91% sensitivity and 81% specificity 4.
- In children with no baseline creatinine, impaired kidney function is defined as serum creatinine greater than twice the upper limit of normal for age and sex 5.
Bottom Line
This creatinine value of 0.45 mg/dL is reassuring and consistent with normal kidney function in an 11-year-old child. No further workup is indicated unless there are clinical signs of kidney disease, abnormal urinalysis findings, or other concerning features 5, 4.