A urinalysis identifies a negative result for reducing sugars, yet the test for glucose (glucose oxidase reaction) was positive on the dipstick. What do these results suggest?
A. The urine collection container was cleaned with bleach
B. This may suggest that the patient has galactosemia
C. The patient is on mega doses of ascorbic acid.
D. There is an analytic error in the testing.
The correct answer and explanation is:
The correct answer is D. There is an analytic error in the testing.
Explanation:
A urinalysis that shows a negative result for reducing sugars but a positive result for glucose on the dipstick suggests a possible analytic error in the testing procedure. Typically, the dipstick test for glucose uses glucose oxidase, which is specific to glucose. It will react with glucose in the urine, producing a color change to indicate the presence of glucose.
However, the reducing sugars test detects a variety of sugars, including glucose and other reducing sugars like galactose. If the reducing sugars test is negative, but the dipstick test for glucose is positive, it may indicate a problem with the test method or reagents used. Several factors can cause this discrepancy, such as:
- Inadequate reagent activity: The glucose oxidase reaction could have worked incorrectly or overreacted to substances in the urine that aren’t glucose.
- Test contamination: The test strip or the specimen may have been contaminated with substances that cause false results.
- Improper handling of the test sample: Factors like temperature or improper storage of the test strip or urine sample may lead to errors in the test.
- Interference from other substances: Ascorbic acid or other substances in the urine could also interfere with the results. However, a positive result for glucose would generally not occur in this case unless the interference is significant enough to affect the specific test for glucose without affecting the reducing sugars test.
Other options:
- A. The urine collection container was cleaned with bleach: While bleach can sometimes interfere with tests, it wouldn’t typically cause this particular pattern of results (negative reducing sugars and positive glucose).
- B. This may suggest that the patient has galactosemia: Galactosemia is a condition that involves an inability to metabolize galactose, which would typically cause positive results in the reducing sugars test. This option is not consistent with the results.
- C. The patient is on mega doses of ascorbic acid: High levels of ascorbic acid can interfere with some tests, but it wouldn’t cause the specific combination of results described here.
Therefore, D is the most plausible explanation for the situation.