From the Guidelines
The presence of WBC esterase +1 and epithelial cells on a urinalysis does not automatically indicate a urinary tract infection (UTI) and should not be used as the sole basis for diagnosis or treatment. These findings alone are insufficient for a UTI diagnosis, as they can occur due to contamination, inflammation, or other non-infectious causes 1. A true UTI diagnosis typically requires both symptoms (such as painful urination, frequency, urgency, or suprapubic pain) and laboratory evidence of significant bacteriuria.
Some key points to consider in the diagnosis of UTI include:
- The presence of pyuria and/or bacteriuria on urinalysis, as well as a positive urine culture with at least 50,000 colony-forming units (cfu) per milliliter of a uropathogen obtained through transurethral catheterization or suprapubic aspiration (SPA) 1
- The WBC esterase +1 represents only a mild elevation of white blood cells, which can occur due to contamination, inflammation, or other non-infectious causes
- Epithelial cells in the urine sample often indicate contamination during collection, particularly if they are squamous epithelial cells from the genital area
- For a more definitive UTI diagnosis, clinicians should look for higher levels of WBC esterase (≥2+), positive nitrites, significant bacteriuria on microscopy (>5 WBCs per high-power field), and a positive urine culture with >100,000 colony-forming units of a uropathogen
Without these additional findings and clinical symptoms, treatment for UTI based solely on +1 WBC esterase and epithelial cells could lead to unnecessary antibiotic use and potential development of resistance. It is essential to consider the clinical context and obtain a high-quality urine specimen through transurethral catheterization or SPA to confirm the diagnosis of UTI 1.
From the Research
Urine Test Results and UTI Diagnosis
- A positive result for leukocyte esterase (+1) and the presence of epithelial cells in a urine test do not necessarily indicate a urinary tract infection (UTI) 2, 3, 4.
- The sensitivity and specificity of urine tests, including leukocyte esterase and nitrite, can vary depending on the population being tested and the criteria used to define a positive result 3, 4, 5.
- Studies have shown that the presence of pyuria (white blood cells in the urine) can be a more reliable indicator of UTI than leukocyte esterase or nitrite tests alone 4, 5.
Diagnostic Value of Urine Tests
- A systematic review and meta-analysis found that urine sediment microscopy and automated urinalysis had higher sensitivity and specificity for detecting UTI than routine urine dry chemical methods 5.
- The use of microfluidic paper-based devices has been explored for the quantitative detection of leukocyte esterase in urine, with promising results 6.
- However, the diagnostic value of these tests can depend on various factors, including the population being tested and the criteria used to define a positive result 2, 3, 4, 5.
Limitations of Urine Tests
- Urine tests, including leukocyte esterase and nitrite, are not always accurate in detecting UTI, and false positives or false negatives can occur 2, 3, 4, 5.
- The presence of epithelial cells in a urine test can be a contaminant and does not necessarily indicate a UTI 2.
- Therefore, urine test results should be interpreted in the context of clinical symptoms and other diagnostic criteria to confirm a diagnosis of UTI 2, 3, 4, 5.