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Urinary phosphate/creatinine, calcium/creatinine, and magnesium/creatinine ratios in a healthy pediatric population
V Matos1, G van Melle, O Boulat
1Service de Pédiatrie, Institut Universitaire de Médecine Sociale et Préventive, Lausanne, Switzerland.
Insights
This study establishes reference values for urinary phosphate/creatinine, calcium/creatinine, and magnesium/creatinine ratios in children aged 1 month to 17 years. These key pediatric reference values decrease significantly with age, providing crucial clinical data.
Area of Science:
- Pediatric Nephrology
- Clinical Chemistry
- Biomarker Research
Background:
- Accurate reference values for urinary solute/creatinine ratios are essential for diagnosing pediatric kidney disorders.
- Existing data for urinary phosphate/creatinine (P/Cr), calcium/creatinine (Ca/Cr), and magnesium/creatinine (Mg/Cr) ratios in infants and children are limited.
- Establishing age-specific reference ranges is crucial for interpreting these biomarkers in pediatric populations.
Purpose of the Study:
- To determine reference values for urinary P/Cr, Ca/Cr, and Mg/Cr ratios in healthy children from 1 month to 17 years.
- To provide comprehensive reference ranges for the second morning urine sample in pediatric age groups.
- To establish age-dependent reference curves for these urinary ratios.
Main Methods:
- Analysis of urinary P/Cr, Ca/Cr, and Mg/Cr ratios from second morning urine samples.
- Inclusion of 410 healthy children aged 1 month to 17 years.
- Statistical analysis using nonlinear regression to establish age-specific reference curves and percentiles.
Main Results:
- Reference values (5th and 95th percentiles) were established for urinary P/Cr, Ca/Cr, and Mg/Cr ratios.
- No significant sex-based differences were observed.
- All three solute/creatinine ratios showed a significant decrease with increasing age, with upper limits declining substantially.
Conclusions:
- Urinary P/Cr, Ca/Cr, and Mg/Cr ratios exhibit strong age-dependent variations in children.
- The study provides validated reference values in both SI and mass units for these urinary ratios.
- These findings are critical for accurate clinical interpretation and diagnosis in pediatric patients.
Objective:
To determine reference values for urinary phosphate/creatinine (Cr) concentration ratios and to complete reference values for urinary calcium/creatinine and magnesium/creatinine ratios in the second morning urine sample of healthy infants, children, and adolescents.
Design:
Urinary P/Cr, Ca/Cr, and Mg/Cr ratios were determined from the second morning urine sample. Two urine samples were obtained 1 week apart from most subjects to assess reproducibility.
Setting:
Kindergartens and schools of Lausanne, Switzerland.
Participants:
A total of 410 healthy children aged 1 month to 17 years (197 girls and 213 boys) participated in the study.
Results:
The 5th and 95th percentiles were estimated from 664 urine samples. There were no differences related to sex. A nonlinear regression in terms of age was used to smooth the estimated percentiles yielding reference curves from which critical values may be obtained for any given age. The 95th percentile for urinary Ca/Cr and Mg/Cr agreed with previously reported values in children older than 7 years. The upper limit of the three solute/creatinine ratios decreased significantly with age: for urinary P/Cr from 19.0 mol/mol at 1 month to 2.7 at 14 years; for urinary Ca/Cr from 2.2 to 0.7 mol/mol, and for urinary Mg/Cr from 2.2 to 0.6 mol/mol. Lower limits varied little. Interindividual and intraindividual variations decreased with age.
Conclusions:
Urinary P/Cr, Ca/Cr, and Mg/Cr ratios vary strongly with age. We provide reference values, expressed both in SI and in mass units, for urinary P/Cr, Ca/Cr, and Mg/Cr in children aged one month to 17 years.