What effect does ascorbic acid have on urine analysis tests?

Ascorbic acid, commonly known as vitamin C, has a significant impact on urine analysis tests, particularly in its ability to interfere with the detection of certain substances. When present in high concentrations in the urine, ascorbic acid functions as a reducing agent, which can lead to false negative results in tests for glucose, nitrites, and certain other analytes. This interference occurs because ascorbic acid can react with the chemical reagents used in these tests, masking the presence of glucose or other substances that would normally be detected.

For example, in glucose testing, if ascorbic acid is present, it may prevent the glucose oxidase reaction from occurring, making it appear as though glucose is not present in the urine when it actually is. Similarly, in nitrate testing, ascorbic acid can reduce nitrite, causing a false negative result, which is particularly crucial in diagnosing urinary tract infections.

Understanding this effect is vital for laboratory personnel and clinicians because it helps them interpret test results accurately and consider the potential influence of dietary factors and supplementation on urine composition. This insight enables better clinical decision-making and more reliable patient management based on urine analysis findings.