Determination of oxalate excretion in spot urines of healthy children by ion chromatography

Abstract

Summary:Evidence for the suitability of Spot urines for selective screening in children was obtained by comparing the 24-hour urinary oxalate excretion with the ratio of urinary oxalate to creatinine [mmol/mol] in spontaneously voided urine samples. Spot urines of 169 healthy children aged l day to 13 years were analysed in order to establish reference values for the urinary oxalate/creatinine ratio in relation to age and body surface area. Oxalate was measured by automated ion chroraatography. Results showed an inverse relationship between the oxalate/creatinine ratio and age. The highest ratios, 131 ± 57 mmol/mol (mean ± 2 SD), were found in infants. At age two years, the ratio was 84 ± 55, at age five years 56 ± 35, and for children older than ten years 42 ± 31. This finding can be explained by the gain of muscle mass and hence increased creatinine productiori with increasing age. Data for the urinary oxalate/creatinine ratio are presented according to body surface area for the assessment of children with abnormal growth. In 19 urine samples from nine patients with primary hyperoxaluria, the oxalate/creatinine ratio greatly exceeded (286-2022 mmol/mol) the above reference ranges. We therefore propose the determination of the oxalate/creatinine ratio in spot urines for the selective screening for hyperoxaluria in children with nephrocalcinosis or urolithiasis.

The comparability of oxalate excretion and oxalate:creatinine ratio in the investigation of primary hyperoxaluria: review of data from a referral centre

“…The age dependence of urine oxalate is well known 17–19 and our data confirmed a rapid fall in oxalate:creatinine ratio over the first few years of life (Figure 1). Rapid growth and increase in muscle mass leads to larger creatinine production and hence excretion, therefore oxalate:creatinine ratio in urine decreases.…”

Evaluation of a high‐performance liquid chromatography method for urinary oxalate determination and investigation regarding the pediatric reference interval of spot urinary oxalate to creatinine ratio for screening of primary hyperoxaluria

“…Subsequently, based on median splits presented in Table 4 and the specific milk‐dominated diet composition of infants <6 months of age, participants were re‐divided into four groups (<0.5, 0.5–2, 2–8, and 8–17 years of age) for the establishment of RIs (Table 5; 0–0.5 years: <379 mmol/mol Cr, 0.5–2 years: <192 mmol/mol Cr, 2–8 years: <165 mmol/mol Cr, 8–17 years: <75 mmol/mol Cr). The age‐dependent decrease in oxalate levels in pediatric subjects is consistent with earlier reports that used different methodologies 23,24 . Cochat et al reported the age‐related RI of oxalate in random urine (<1 year: 15–260 mmol/mol Cr, 1–5 years: 11–120 mmol/mol Cr, 5–12 years: 60–150 mmol/mol Cr, >12 years: 2–80 mmol/mol Cr) and the URL values were primarily consistent with the quantile regression equation (URL = −13.1398 years + 261.826 mmol/mol Cr) 1 .…”

Clearance and removal of oxalate in children on intensified dialysis for primary hyperoxaluria type 1

“…All samples of whole dialysate were stored at 41C in a plastic tank over 24 h. After mixing, samples of 10 ml were taken and stored at À201C for 24 h maximum before measurement. After 10-fold dilution with 0.3 mol/l boric acid, oxalate concentration was measured by a modified ion chromatography method as described by von Schnakenburg et al 16 Urine collection over 24 h, preparation of samples, and analysis of oxalate concentration was handled likewise. Blood samples of 2 ml were placed in ice-cooled heparinized vials and immediately centrifuged at 1000 g for 10 min at 41C.…”