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Evaluation of variability of proteinuria indices
M Yoshimoto1, H Tsukahara, M Saito
1Department of Paediatrics, Fukui Medical School, Japan.
Insights
The protein/creatinine ratio (Up/Ucr) in early morning urine samples is a reliable and simple indicator for assessing proteinuria in children. This method shows less variability compared to other urine tests, making it a superior choice for clinical use.
Area of Science:
- Pediatric Nephrology
- Clinical Chemistry
- Biomarker Validation
Background:
- Accurate assessment of proteinuria is crucial for diagnosing and managing kidney diseases in children.
- Various indices exist for measuring proteinuria, but their reliability and practicality in pediatric populations require further evaluation.
Purpose of the Study:
- To compare the accuracy and variability of different proteinuria indices in children.
- To determine the most reliable and practical index for assessing 24-hour urinary protein excretion (24 h-Up) in pediatric patients.
Main Methods:
- Compared protein concentration, hourly protein excretion rate (Up/h), and protein/creatinine ratio (Up/Ucr) against 24 h-Up in 44 children (aged 4-16 years).
- Analyzed single voided urine samples and 24-hour collections.
- Assessed variability of indices using morning, bedtime, and daytime samples from 39 subjects.
Main Results:
- Excellent correlation was found between Up/h and Up/Ucr in early morning samples, closely matching 24 h-Up.
- Up/Ucr demonstrated significantly less variability than Up/h in daytime and bedtime samples.
- Urinary protein concentration showed poorer correlation with 24 h-Up and higher variability compared to other indices.
Conclusions:
- The protein/creatinine ratio (Up/Ucr) in early morning urine samples is a superior index for assessing proteinuria in children.
- This index offers simplicity and low day-to-day variability, making it a practical and reliable diagnostic tool.
Abstract:
We compared several indices of proteinuria, namely protein concentration, hourly protein excretion rate (Up/h) and protein/creatinine ratio (Up/Ucr) in single voided urine samples as well as 24 h-urinary protein excretion (24 h-Up), in 44 children, aged 4-16 years, with varying degrees of urinary protein excretion. We found an excellent correlation between Up/h and Up/Ucr in early morning samples. These two indices in early morning samples had excellent correlation with 24 h-Up, comparable to those in any other urine sample of the day. Among daytime samples, Up/h varied widely, in contrast to Up/Ucr, which had significantly less variability. We analysed six early morning and six bedtime samples from 39 of these subjects, and found smaller coefficients of variation for individual patient's indices in morning samples. Up/h was more variable than Up/Ucr, especially in bedtime samples. Urinary protein concentration had a poorer correlation with 24 h-Up and was more variable than any other index. We conclude that the Up/Ucr in early morning samples, which has the advantages both of simplicity and low day-to-day variability in a given patient, is a superior index of proteinuria.