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Difference in urinary protein-to-creatinine ratio using the benzethonium chloride and pyrogallol red methods in
Rintaro Koide1, Hiroyuki Ikeda1, Satoko Takahashi1
1Department of Pediatrics, Japanese Red Cross Narita Hospital, Chiba, Japan.
Insights
The benzethonium chloride (BC) method yields higher urinary protein-to-creatinine ratio (PCR) values than the pyrogallol red (PR) method in children. New reference values are suggested for BC-PCR, emphasizing the need to specify the assay method used.
Area of Science:
- Pediatric Nephrology
- Clinical Chemistry
- Biomarker Assays
Background:
- The protein-to-creatinine ratio (PCR) is a key indicator for proteinuria.
- Different urinary protein assay methods, such as pyrogallol red (PR) and benzethonium chloride (BC), may yield varying PCR results.
- Establishing accurate reference values is crucial for correct proteinuria diagnosis in children.
Purpose of the Study:
- To evaluate the difference between BC-based PCR (BC-PCR) and PR-based PCR (PR-PCR) values in pediatric urine samples.
- To determine if a change in assay method necessitates updated reference values for proteinuria screening in children.
Main Methods:
- Comparison of BC-PCR and PR-PCR values from first-morning urine samples in school-aged children without significant proteinuria.
- Setting the upper limit of reference values at the 97.5th percentile.
- Analysis of urinary protein (UP) and creatinine concentrations using both BC and PR assay methods.
Main Results:
- BC-PCR values were consistently higher than PR-PCR values (mean difference: 0.090 g/gCr).
- A linear relationship was observed between BC-UP and PR-UP concentrations, with BC-UP being higher.
- Suggested BC-PCR reference values for proteinuria were 0.25 g/gCr for elementary and 0.17 g/gCr for junior high school students, which are higher than PR-PCR values.
Conclusions:
- The choice of urinary protein assay method significantly impacts PCR values.
- It is essential to specify the assay method (BC or PR) when reporting PCR results.
- Further research is needed to validate the proposed BC-PCR reference values for pediatric proteinuria screening.
Background:
The appropriate reference value of the urinary protein-to-creatinine ratio (PCR) for proteinuria may change when the urinary pyrogallol red (PR) protein assay method is changed to the benzethonium chloride method (BC). This study aimed to evaluate the difference between BC-based PCR (BC-PCR) and PR-based PCR (PR-PCR) values in children.
Methods:
We compared the BC-PCR and PR-PCR values in the same first-morning urine samples without significant proteinuria in school urine screening settings. The upper limit of the reference values was set at the 97.5th percentile.
Results:
Notably, 133 samples from 124 individuals (female: 62%, age: median 12.3 years, range 6.3-16.9 years) were collected between August 2020 and October 2022. The diagnoses included 34 normal individuals and 99 with asymptomatic hematuria. The urinary protein (UP) concentrations measured using the BC (BC-UP) and PR (PR-UP) methods were in a linear relationship; however, the BC-UP concentrations were higher than the PR-UP concentrations (mean of differences: 11.2, 95% confidence interval (CI): 11.0-13.4 mg/dL). Also, the BC-PCR values were higher than the PR-PCR values (mean of differences: 0.090, 95% CI: 0.082-0.098 g/gCr). The BC-PCR showed a body-size-related decrease, reflecting a body-size-related urinary creatinine increase. The suggested BC-PCR reference values for proteinuria were 0.25 and 0.17 g/gCr for elementary (6-12.4 years) and junior high school students (12.5-16 years), respectively. These values were higher than those of the PR-PCR and need further studies.
Conclusions:
When evaluating PCR results, the urinary protein assay should be stated.
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