Investigations of ascorbic acid interference in urine test strips

Area of Science:

• Clinical Chemistry
• Urinalysis
• Diagnostic Test Development

Background:

• Ascorbic acid (vitamin C) in urine can interfere with standard urinalysis tests.
• This interference can lead to false-negative results, potentially causing critical clinical findings like low glucose or hemoglobin levels to be missed.
• Routine monitoring of ascorbic acid levels or using interference-resistant tests is crucial for accurate urinalysis.

Purpose of the Study:

• To evaluate the impact of ascorbic acid on common 10-parameter urine test strips.
• To identify urine test strips that are largely resistant to ascorbic acid interference.
• To ensure reliable detection of key urinary analytes in the presence of varying ascorbic acid concentrations.

Main Methods:

• Comparison of five common 10-parameter urine test strips from different manufacturers.
• Testing strip performance with clinically relevant concentrations of glucose, hemoglobin, and erythrocytes.
• Assessing interference using varying concentrations of ascorbic acid (up to 1000 mg/L).

Main Results:

• Only Roche Diagnostics' Combur-Test strips demonstrated significant resistance to ascorbic acid interference.
• Clinically relevant low concentrations of erythrocytes, hemoglobin, and glucose were accurately detected with up to 400 mg/L ascorbic acid.
• Higher analyte concentrations were correctly identified even with up to 1000 mg/L ascorbic acid.

Conclusions:

• Ascorbic acid interference is a significant issue with many standard urine test strips.
• Combur-Test offers a reliable solution for accurate urinalysis in the presence of high ascorbic acid levels.
• Using ascorbic acid-resistant test strips like Combur-Test improves diagnostic accuracy and patient safety.