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Age-related reference values for free amino acids in first morning urine specimens
P R Parvy1, J I Bardet, D M Rabier
1Laboratoire de Biochimie Médicale B, Hôpital Necker-Enfants Malades, Paris, France.
Insights
This study establishes age-specific reference values for urinary free amino acids in children. Most amino acid levels decrease with age, aiding in diagnosing aminoacidopathies and tubulopathies.
Area of Science:
- Biochemistry
- Pediatric Nephrology
- Clinical Chemistry
Background:
- Accurate reference ranges for urinary free amino acids are crucial for diagnosing metabolic and kidney disorders in children.
- Existing data on age-related changes in urinary amino acid excretion is limited, particularly for specific age strata.
Purpose of the Study:
- To establish normative, age-related reference values for urinary free amino acids in a pediatric population.
- To provide data that can aid in the clinical interpretation of aminoaciduria and aminoacidemias.
- To investigate the impact of age on the excretion of specific amino acids in urine.
Main Methods:
- Analysis of first morning urine specimens from 360 healthy children across nine distinct age groups (birth to >13 years).
- Quantification of urinary free amino acids using standardized laboratory methods.
- Calculation of reference values expressed as mmol/mol creatinine.
Main Results:
- Established age-specific reference ranges for 15 urinary free amino acids.
- Demonstrated a significant decrease in the concentration of most amino acids with increasing age.
- Identified taurine and 3-methylhistidine as exceptions, showing different age-related patterns.
Conclusions:
- The study provides essential age-related reference data for urinary free amino acids in children.
- These reference values can improve the diagnostic accuracy for aminoacidopathies and renal tubulopathies.
- Understanding these age-dependent changes is vital for pediatricians and clinical chemists.
Abstract:
We determined age-related reference values for urinary free amino acids (in mmol/mol creatinine) in first morning urine specimens from 360 control subjects who were divided into nine age groups: birth to 1 month, 1-6 months, 6-12 months, 1-2 years, 2-4 years, 4-7 years, 7-10 years, 10-13 years, and older than 13 years. Except for taurine and 3-methylhistidine, the concentration of all the amino acids decreased with increasing age. The use of these results to detect aminoacidopathies and tubulopathies is discussed.