What is the normal value of leukocyte (white blood cell) esterase in urine?

From the Guidelines

The normal value of leukocyte esterase in urine is negative or absent, as indicated by the absence of a color change on the dipstick test strip. A negative result suggests that there are no significant amounts of white blood cells in the urine sample, which is the expected finding in healthy individuals. Leukocyte esterase is an enzyme present in white blood cells, particularly neutrophils, and its detection in urine suggests the presence of these inflammatory cells 1.

When urine is tested using a dipstick, the leukocyte esterase pad should not change color if the result is normal. A positive result (typically indicated by a purple color change on the test strip) suggests urinary tract inflammation or infection. The test is commonly performed as part of a routine urinalysis and serves as a screening tool for urinary tract infections. The presence of leukocyte esterase often prompts further investigation, including microscopic examination of the urine sediment or urine culture to identify potential pathogens.

Some key points to consider when interpreting leukocyte esterase results include:

• The sensitivity of the leukocyte esterase test is 94% when used in the context of clinically suspected UTI 1
• The absence of leukocyte esterase in the urine of individuals with asymptomatic bacteriuria is an advantage of the test, rather than a limitation, because it distinguishes individuals with asymptomatic bacteriuria from those with true UTI 1
• The test should be used in conjunction with other diagnostic tools, such as urine culture and microscopic examination, to confirm the presence of a urinary tract infection.

Overall, a negative leukocyte esterase result is a good indicator of the absence of significant urinary tract inflammation or infection, while a positive result should prompt further investigation to confirm the diagnosis.

From the Research

Normal Value of Leukocyte Esterase in Urine

The normal value of leukocyte esterase in urine is not explicitly stated in the provided studies, but we can infer the following information:

• Leukocyte esterase is a marker used to detect urinary tract infections (UTIs) 2, 3, 4, 5, 6
• The presence of leukocyte esterase in urine can indicate pyuria, which is a sign of UTI 2
• The sensitivity and specificity of leukocyte esterase dipstick tests vary across different studies, ranging from 63.6% to 96.4% sensitivity and 44.2% to 95.8% specificity 2, 5

Leukocyte Esterase Detection Methods

Different methods are used to detect leukocyte esterase in urine, including:

• Dipstick tests, which can detect the presence of leukocyte esterase and nitrite in urine 2, 4, 5, 6
• Microfluidic paper-based devices, which can quantitatively detect leukocyte esterase in urine 3
• Microscopic examination, which can detect the presence of leukocytes in urine 2

Quantitative Detection of Leukocyte Esterase

The quantitative detection of leukocyte esterase in urine can be achieved using microfluidic paper-based devices, which can detect concentrations between 2 to 32 (×5.2 U mL-1) 3

• The minimum detectable concentration of leukocyte esterase in urine using this method is 1 (×5.2 U mL-1) 3

Clinical Applications

Leukocyte esterase dipstick tests are commonly used in clinical settings to screen for UTIs, particularly in pediatric patients 4, 5

• The tests can help avoid unnecessary urine cultures and reduce costs 4
• However, the accuracy of the tests can vary depending on the population being tested and the presence of underlying conditions such as congenital anomalies of the kidney and urinary tract (CAKUT) 5