What is the clinical significance of a positive urine leukocyte esterase (LE) test?

From the Guidelines

A positive urine leukocyte esterase (LE) test is a significant indicator of urinary tract infection (UTI) and warrants further investigation, as it has a sensitivity of 72-97% and specificity of 41-86% for detecting UTIs 1. The clinical significance of a positive urine LE test lies in its ability to detect the presence of white blood cells in the urine, which is a common indicator of UTIs. The test is particularly useful as a screening tool, with a high sensitivity for detecting UTIs.

• The sensitivity of the LE test ranges from 72-97%, making it a reliable indicator of UTIs 1.
• The specificity of the LE test ranges from 41-86%, which means that false positives can occur, but the test is still useful for screening purposes 1.
• When the LE test is positive, especially when accompanied by nitrites (which indicate bacteria), clinical symptoms should be assessed and a urine culture may be ordered to identify the specific pathogen and determine antibiotic sensitivity.
• False positives can occur with contaminated specimens, certain medications, or high vitamin C intake, while false negatives may happen with high protein or glucose levels, or certain antibiotics.
• The LE test is performed using a dipstick that changes color in the presence of leukocyte esterase, with results typically reported as negative, trace, small, moderate, or large. The LE test provides valuable information for rapid clinical decision-making regarding potential UTIs, and its results should be interpreted in conjunction with clinical symptoms and other diagnostic tests to ensure accurate diagnosis and treatment.
• A study published in the Journal of the American Medical Association (JAMA) found that the presence of leukocyte esterase or nitrite in the urine had a sensitivity of 88% and a specificity of 79% for detecting UTIs 1.
• Another study published in the Annals of Emergency Medicine found that a positive LE test had a positive predictive value of 46% and a negative predictive value of 96% for detecting UTIs 1.

From the Research

Clinical Significance of a Positive Urine Leukocyte Esterase (LE) Test

• A positive urine leukocyte esterase (LE) test is a significant indicator of urinary tract infection (UTI) 2, 3, 4, 5.
• The sensitivity of the LE test varies across studies, with reported values ranging from 48.5% to 100% 3, 4, 5.
• The specificity of the LE test also varies, with reported values ranging from 44.2% to 76% 2, 3.
• The combination of LE and other tests, such as nitrite and blood, can increase the sensitivity and specificity of UTI diagnosis 4, 5.
• A positive LE test can be used as a screening tool to identify patients who require further testing, such as urine culture, to confirm the diagnosis of UTI 3, 5.
• The quantitative determination of LE can be useful in establishing a diagnosis of UTI, and microfluidic paper-based devices have been developed for this purpose 6.

Diagnostic Accuracy of LE Test

• The LE test has been shown to be a valuable screening test for UTI, with a high sensitivity and moderate specificity 3.
• The test can be used to detect pyuria, which is a significant indicator of UTI 2, 5.
• The combination of LE and pyuria can increase the diagnostic accuracy of UTI diagnosis 2.
• The LE test can be used in conjunction with other tests, such as urine culture, to confirm the diagnosis of UTI 3, 4, 5.

Clinical Applications of LE Test

• The LE test can be used as a rapid and simple screening technique for detecting UTI in outpatient and inpatient settings 3, 4, 5.
• The test can be used to identify patients who require further testing, such as urine culture, to confirm the diagnosis of UTI 3, 5.
• The LE test can be used to monitor the effectiveness of treatment for UTI 6.
• The test can be used in conjunction with other tests, such as urine culture, to guide antibiotic therapy for UTI 5.