To evaluate the effect of ascorbic acid on some tests (glucose, blood and leukocyte
esterase) by comparing strips that are resistant to its interference and those that measure ascorbic acid.
Material and Methods: We retrospectively investigated urine results of 10055 consecutive patients. We
performed urine pools from samples that were negative for various amounts of glucose or blood or leukocyte esterase. To each sample, different amounts of ascorbic acid were added, adjusted to give
final concentrations of 10, 25, 50, 100, 200 and 400 mg/dL.
Results: Ascorbic acid was positive in 9.2% of 10055 urine samples, and 50% of those came from the
emergency department and 51% of the patients were children. 70% of patients had 10 mg/dL ascorbic
acid concentration. Resistant dipstick to ascorbic asid interference did not show negative interference
for glucose when its concentration is 100 mg/dL or less. Although ascorbic acid showed interference on
urine dipstick blood test, the results were not negative. Test strips that measure ascorbic acid showed
negative interference when the leukocyte esterase, blood and glucose concentrations are >50 mg/dL,
≥10 mg/dL ve ≥25 mg/dL, respectively.
Conclusion: Concentration of 10 mg/dL ascorbic acid is sufficient to interfere dipstick blood test and
repeating a test is not appropriate after restriction of vitamin C consumption in emergency conditions.
Therefore, resistant dipstick to ascorbic acid may preferable. However, it is necessary to determine the
ascorbic acid concentration that these strips are resistant.