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Urinary oxalate and urate to creatinine ratios in a healthy pediatric population
V Matos1, G Van Melle, D Werner
1Department of Pediatrics, Centre Hospitalier Universitaire Vaudois (CHUV), Lausanne, Switzerland.
Insights
This study establishes reference ranges for urinary oxalate and urate to creatinine ratios in children. These findings provide crucial data for assessing kidney health in pediatric populations.
Area of Science:
- Pediatric Nephrology
- Clinical Chemistry
- Biomarkers of Kidney Health
Background:
- Urinary oxalate and urate levels are important indicators of kidney function and metabolic health.
- Establishing age-specific reference ranges is crucial for accurate diagnosis and monitoring in children.
- Existing reference data for pediatric urinary oxalate and urate to creatinine ratios is limited.
Purpose of the Study:
- To determine reference percentiles for urinary oxalate (UOx) to creatinine (Cr) and urate (UUra) to creatinine (Cr) ratios.
- To establish age-dependent reference curves for these ratios in healthy infants, children, and adolescents.
- To provide a normative dataset for clinical interpretation of pediatric urine tests.
Main Methods:
- Analysis of spontaneously voided second morning urine samples from 384 healthy children (1 month to 17 years).
- Determination of urinary oxalate, urate, and creatinine concentrations using standard analytical chemical techniques.
- Statistical analysis including nonlinear regression to generate age-smoothed 5th and 95th percentile curves.
Main Results:
- Reference percentile curves for UOx/Cr and UUra/Cr ratios were established for different age groups.
- The 95th percentile for UOx/Cr decreased with age, reaching adult levels by 7 years.
- The 95th percentile for UUra/Cr decreased more gradually, stabilizing in adolescence.
Conclusions:
- The study provides essential age-specific reference values for urinary oxalate and urate to creatinine ratios in children.
- These reference curves aid in the early detection and management of pediatric kidney conditions.
- The data supports the use of second morning void urine samples for routine pediatric urinalysis.
Abstract:
The purpose of the study was to determine reference percentiles for the urinary (U) oxalate (Ox) and urate (Ura) to creatinine (Cr) concentration ratios in the second morning urine of healthy infants, children, and adolescents. The urinary oxalate and urate to creatinine ratios were determined in the spontaneously voided second morning urine sample. To test reproducibility, two urine samples were analyzed on 2 consecutive weeks in 63% of the subjects. Three hundred eighty-four healthy children (181 girls, 203 boys), aged 1 month to 17 years, from nurseries, kindergartens, and schools of Lausanne, Switzerland, were studied. The 5th and 95th percentiles were determined from the total number of urine samples (627) after confirmation that there was no order effect between repeated measurements and there were no significant sex differences. A nonlinear regression analysis in terms of age was used to smooth the calculated percentiles. In this manner, curves were obtained from which the reference values can be read at any given age. The 95th percentiles decreased with age: for UOx/Cr from 0.175 mg/mg (0.22 mol/mol) at 1 to 6 months to 0.048 mg/mg (0.06 mol/mol) from 7 years and beyond; and UUra/Cr from 2.378 mg/mg (1.6 mol/mol) at 1 to 6 months to 0.594 mg/mg (0.4 mol/mol) in adolescence. We provide 5th and 95th percentile curves for the UOx/Cr and UUra/Cr ratios determined from the second morning urine samples in a large cohort of healthy infants, children, and adolescents. Values were determined by standard analytical chemical techniques and were analyzed by powerful statistical methods. The calculated 95th percentile for the UOx/Cr values fell rather rapidly and reached normal adult values by the age of 7 years, whereas for UUra/Cr, the 95th percentile decreased slowly and stabilized in adolescence.