Continuous-flow assay for urinary oxalate using immobilised oxalate oxidase

Area of Science:

• Biochemistry
• Analytical Chemistry
• Clinical Diagnostics

Background:

• Oxalate is a key metabolite linked to kidney stone formation.
• Accurate and efficient measurement of urinary oxalate is crucial for diagnosis and management.
• Existing methods may have limitations in speed, sensitivity, or complexity.

Purpose of the Study:

• To develop and validate a continuous-flow assay for quantifying urinary oxalate.
• To assess the assay's accuracy, sensitivity, reproducibility, and speed.
• To compare the new assay with an established enzymatic method.

Main Methods:

• Utilized covalently attached oxalate oxidase (EC 1.2.3.4) for oxalate oxidation.
• Employed a colorimetric detection of hydrogen peroxide using horseradish peroxidase (EC 1.11.17), MBTH, and DMAB.
• Incorporated sodium nitrite treatment to eliminate ascorbate interference.

Main Results:

• Demonstrated high accuracy with 93% +/- 11% recovery of added oxalate.
• Achieved a sensitive detection limit of 1.0 mumol/L.
• Exhibited excellent reproducibility (within-batch CV 3.5%, between-batch CV 5%) and a rapid throughput of 15 samples/h.
• Showed strong correlation (R = 0.99) with an established enzymatic method.

Conclusions:

• The developed continuous-flow assay provides an accurate, sensitive, and reproducible method for urinary oxalate determination.
• This assay is suitable for routine clinical use due to its efficiency and reliability.
• The method offers a valuable alternative to existing oxalate measurement techniques.