From the Guidelines
Leukocyte esterase in urine is a crucial marker for detecting urinary tract infections (UTIs) and should be used as a screening tool in conjunction with other diagnostic methods, such as urine culture and microscopic examination for white blood cells (WBCs) and bacteria, as recommended by the Infectious Diseases Society of America 1. The presence of leukocyte esterase in urine indicates the presence of white blood cells, suggesting inflammation or infection in the urinary tract. When detected on a urine dipstick test, it serves as a screening tool for UTIs. The test works by detecting enzymes produced by neutrophils, which are the most common type of white blood cells that respond to bacterial infections. A positive leukocyte esterase result often correlates with pyuria (white blood cells in urine) and should prompt further investigation, especially when accompanied by symptoms like burning during urination, frequency, or urgency. However, false positives can occur due to contamination during collection, while certain conditions like high vitamin C intake may cause false negatives. The test is particularly valuable in clinical settings for its rapid results, allowing for prompt initiation of appropriate antibiotic therapy for UTIs before culture results become available. For suspected UTIs with positive leukocyte esterase, empiric treatment often includes antibiotics like nitrofurantoin, trimethoprim-sulfamethoxazole, or fluoroquinolones, depending on patient factors and local resistance patterns. Some key points to consider when interpreting leukocyte esterase results include:
- The sensitivity and specificity of the test, with a sensitivity of 88% and false positive rate of 7% for urinary tract infection, as reported in a meta-analysis 1.
- The importance of using the test in conjunction with other diagnostic methods, such as urine culture and microscopic examination for WBCs and bacteria, as recommended by the Infectious Diseases Society of America 1.
- The need to consider patient factors, such as age, sex, and underlying medical conditions, when interpreting test results and determining the likelihood of UTI, as noted in the clinical practice guideline for the diagnosis and management of the initial UTI in febrile infants and children 2 to 24 months 1.
From the Research
Significance of Leukocyte Esterase in Urine
- Leukocyte esterase is a useful marker for diagnosing urinary tract infections (UTIs) 2, 3
- The presence of leukocyte esterase in urine can indicate pyuria, which has a high sensitivity and specificity for positive urine culture 2
- A dipstick test for leukocyte esterase can be used as a diagnostic tool for detecting UTIs, with a sensitivity of 63.6% and a specificity of 44.2% 2
- Microfluidic paper-based devices can be used for the quantitative detection of leukocyte esterase in urine, with a minimum detectable concentration of 1 (×5.2 U mL-1) 3
Diagnostic Accuracy
- The combination of leukocyte esterase and nitrite tests can improve the diagnostic accuracy of UTIs, with a sensitivity of 66.7% 2
- Pyuria can be used to detect UTIs instead of urine culture due to its significant incidence and high sensitivity (95.6%) and specificity (60.9%) 2
- The diagnostic accuracy of leukocyte esterase can be improved by using microfluidic resistance sensors based on silver ink and silver ink mixed with ZnO nanoparticles 3
Clinical Applications
- Leukocyte esterase can be used as a diagnostic tool in detecting UTI cases, especially in outpatient clinics 2
- The quantitative detection of leukocyte esterase can be used to monitor the progression of UTIs and the effectiveness of treatment 3
- The use of leukocyte esterase as a diagnostic marker can help reduce the reliance on urine culture and improve the efficiency of UTI diagnosis 2, 3