Canadian Society for Medical Laboratory Science (CSMLS) Practice Exam

Which substance is detected by urine dipstick tests for bacteria?

1. Nitrates

2. Phosphates

3. Nitrites

4. None of the above

The correct answer is: Nitrites

Urine dipstick tests are commonly used to screen for urinary tract infections and provide information about the presence of certain substances in urine. Among these substances, nitrites are specifically detected when bacteria that reduce nitrates to nitrites are present in the urine. When bacteria such as E. coli are present in the urinary tract, they can convert nitrates (which are usually present in urine) into nitrites. The dipstick test contains reagents that react with nitrites, resulting in a color change that indicates their presence. This makes nitrite detection a useful indicator of bacterial infection in the urinary system. In contrast, phosphates do not play a significant role in the detection of bacterial presence, nor are they typically part of routine dipstick tests for this purpose. Additionally, while nitrates are present in urine and can contribute to nitrite formation, the dipstick test specifically identifies nitrites as an indicator of bacterial activity. Therefore, the correct answer reflects the specific substance that the test detects in relation to bacterial infections in the urinary tract.