A high urine uric acid level (1575 mg/day) affects urine glucose measurement by the glucose oxidase/peroxidase method in which way?

• A. Urine glucose level will be falsely low.
• B. Urine glucose level will be falsely high.
• C. Urine glucose level will be accurate.
• D. Urine glucose level will exceed the linearity of the method.

Answer: (A)

Colorimetric glucose measurements with glucose oxidase and peroxidase rely on glucose being converted to hydrogen peroxide, and then peroxidase uses that hydrogen peroxide to produce a colored product. If uric acid is very high in urine, it can react with or scavenge hydrogen peroxide, reducing the amount available for the peroxidase reaction. That dampens the color signal, so the measured glucose appears lower than it truly is. In other words, uric acid interference causes a falsely low urine glucose result. This effect is about signal reduction from interference, not about increasing the signal or pushing the measurement outside the assay’s linear range.