Are commonly used paediatric reference intervals for water and electrolyte balance appropriate for clinical use?

Area of Science:

• Clinical Chemistry
• Paediatric Nephrology
• Laboratory Medicine

Background:

• Paediatric reference intervals for electrolytes are not well-established.
• A UK initiative proposed a harmonized sodium interval of 133-146 mmol/L for all ages.
• The validity of this broad interval in children requires investigation.

Purpose of the Study:

• To evaluate the appropriateness of the 133-146 mmol/L sodium reference interval in children.
• To analyze age-related differences in paediatric sodium, potassium, and creatinine levels.
• To determine if current paediatric electrolyte distributions align with proposed harmonized intervals.

Main Methods:

• Retrospective analysis of paediatric renal profiles (sodium, potassium, urea, creatinine) from a primary care database over 13 years.
• Filtering of results to include only patients with normal renal function.
• Age-specific analysis of electrolyte concentrations and distribution patterns.

Main Results:

• Paediatric sodium concentrations were lower in infants (mean 138 mmol/L) and increased towards adult levels by teenage years (mean 140 mmol/L).
• Potassium showed a similar age-related pattern, and creatinine increased with age.
• Observed sodium concentration distributions were narrower than the 133-146 mmol/L interval across all paediatric age groups.

Conclusions:

• The proposed 133-146 mmol/L sodium reference interval is likely too broad for paediatric populations.
• More specific, age-adjusted reference ranges are necessary for accurate paediatric electrolyte interpretation.
• Further research is recommended to establish refined paediatric reference intervals for key electrolytes.