If a urine glucose result is 160 mg/dL by one method and 240 mg/dL by another method the next day, what is likely causing this discrepancy?

The discrepancy in urine glucose results is likely due to high levels of reducing substances interfering with the Trinder reaction. The Trinder reaction is a common enzyme-based test that measures glucose levels, and it can be affected by the presence of other reducing substances, which may lead to falsely elevated glucose readings.

In cases where there are significant amounts of other reducing agents present in the urine, the Trinder reaction may not only measure glucose but also be influenced by those substances. This results in variability between different testing methods if one method is more susceptible to interference from these substances than the other.

Therefore, if one test is yielding a much higher glucose concentration, it may be reacting to these interfering agents rather than providing an accurate glucose level. This situation emphasizes the importance of considering the nature of the sample and potential interferences when interpreting results from different testing methodologies.