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Variability in urinary oxalate measurements between six international laboratories
Naim M Maalouf1, Beverley Adams Huet, Andreas Pasch
1Department of Internal Medicine, University of Texas, Southwestern Medical Center, Dallas, TX, USA.
Summary
Urinary oxalate measurement lacks standardization, leading to significant variability between labs. This hinders accurate hyperoxaluria assessment and kidney stone risk evaluation, emphasizing the need for standardized methods.
Area of Science:
- Nephrology
- Clinical Chemistry
- Analytical Chemistry
Background:
- Hyperoxaluria is a primary risk factor for kidney stone formation.
- Accurate urinary oxalate measurement is crucial for kidney stone risk assessment.
- Current methods for urinary oxalate quantification lack standardization.
Purpose of the Study:
- To assess the variability in urinary oxalate measurement across different international laboratories.
- To compare the reliability of different analytical methods for urinary oxalate quantification.
- To highlight the need for standardized protocols in oxalate measurement.
Main Methods:
- Urine samples were analyzed in duplicates by six international laboratories.
- Oxalate, sodium, and creatinine levels were measured using oxalate oxidase kits and high-performance liquid chromatography (HPLC).
- Urine samples were also tested after spiking with a known oxalate concentration.
Main Results:
- Significant inter-laboratory variability in urinary oxalate quantification was observed.
- Oxalate oxidase kits demonstrated more consistent results compared to HPLC-based methods.
- Acidification of samples prior to analysis led to significantly higher oxalate concentrations.
Conclusions:
- Variability in urinary oxalate measurement may contribute to discrepancies in reported hyperoxaluria prevalence.
- Standardization of urinary oxalate measurement methods is urgently required.
- Standardized methods will improve the accuracy of kidney stone risk assessment.
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