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Analyte variations in consecutive 24-hour urine collections in children
Jonathan S Ellison1, John M Hollingsworth2, Craig B Langman3
1Seattle Children's Hospital, WA, USA.
Journal of Pediatric Urology
|July 26, 2017
Summary
Consecutive 24-hour urine collections provide more clinically useful information for pediatric nephrolithiasis evaluation than single collections. Misclassification of stone risk can occur in up to 25% of children with only one urine sample.
Area of Science:
- Pediatric Nephrology
- Urology
- Metabolic Evaluation
Background:
- Metabolic evaluation for pediatric nephrolithiasis typically starts with a single 24-hour urine collection.
- While multiple collections improve adult diagnosis, pediatric data on variability is limited.
Purpose of the Study:
- To assess the variability of consecutive 24-hour urine collections in children at risk for nephrolithiasis.
- To determine if repeat collections offer greater diagnostic value compared to a single collection.
Main Methods:
- A multi-institutional study analyzed data from 733 children under 18 at risk for recurrent nephrolithiasis.
- A subset of patients had two collections within 7 days, with creatinine varying by 10% or less.
- Discordance between collections was evaluated against normative urine chemistry values.
Main Results:
- Over one-third of children showed ≥30% variation in urine calcium or volume between samples.
- Urine oxalate varied more in children under 5.
- Discordance with normative values was highest for urine oxalate (22.5%) and supersaturation ratios (calcium phosphate 25.1%, calcium oxalate 20.5%).
Conclusions:
- Using a single 24-hour urine collection may misclassify stone risk in up to 25% of children.
- Repeat 24-hour urine collections are recommended before interventions to improve diagnostic yield in pediatric nephrolithiasis.
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