From the Guidelines
The most specific laboratory tests to verify a urinary tract infection (UTI) are urinalysis for determination of leukocyte esterase and nitrite level by use of a dipstick and a microscopic examination for WBCs, followed by urine culture (with antimicrobial susceptibility testing) if pyuria (≥10 WBCs/high-power field or a positive leukocyte esterase or nitrite test is present on dipstick) 1.
Key Laboratory Tests
- Urinalysis with dipstick for leukocyte esterase and nitrite level
- Microscopic examination for WBCs
- Urine culture (with antimicrobial susceptibility testing) if pyuria is present
Importance of Proper Specimen Collection
- A mid-stream or clean-catch specimen is ideal for accurate results 1
- For men, a freshly applied, clean condom external collection system may be necessary 1
- For women, in-and-out catheterization may be required 1
Interpretation of Results
- Pyuria (≥10 WBCs/high-power field or a positive leukocyte esterase or nitrite test) suggests infection 1
- Urine culture results typically take 24-48 hours and are considered positive with bacterial growth 1
Clinical Considerations
- Symptoms alone can be misleading, and proper identification of the pathogen ensures appropriate antibiotic selection 1
- Empiric treatment may begin before culture results return, but should be guided by local antimicrobial resistance patterns 1
From the Research
Urinary Tract Infection Verification Labs
The following labs can be used to verify urinary tract infections:
- Urine culture: considered the gold standard for diagnosing UTIs, but results can take up to 24 hours 2
- Urine dipstick analysis: a quick and cheap test that can detect leukocyte esterase, nitrite, and blood in the urine, but has limitations in diagnostic accuracy 3, 4, 5
- Urinalysis: a test that can detect red and white blood cells, bacteria, and other abnormalities in the urine, but may not be as accurate as urine culture 3
Specific Lab Tests
Some specific lab tests that can be used to verify UTIs include:
- Leukocyte esterase test: detects the presence of white blood cells in the urine, with a sensitivity of 48.5% 4
- Nitrite test: detects the presence of nitrite in the urine, with a sensitivity of 23.31% 4
- Blood test: detects the presence of blood in the urine, with a sensitivity of 63.94% 4
Sample Collection Methods
Different sample collection methods can be used to collect urine samples for lab tests, including:
- Midstream urine (MSU) sample: a sample collected from the middle of the urine stream, which can help reduce contamination 6
- Midstream clean-catch (MSCC) sample: a sample collected from the middle of the urine stream, with the genital area cleaned before collection 6
- First-void urine sample: a sample collected from the first void of the day, which can help detect bacteria in the urine 6