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Leukocyte esterase (LE) is a type of urine test that is most commonly used to diagnose urinary tract infection (UTI). The test is also known as WBS esterase. It is used to determine if white blood cells are in the urine, which indicates an infection. More specifically, it looks for the enzyme white blood cells release called esterase. The LE test is often used with a urinary nitrite test to confirm a UTI.
An LE test is painless, quick and non-invasive. In order for the test to be conducted, the patient must provide a clean urine sample. Then a medical professional will place a strip known as a dipstick into the urine. The dipstick has several different color blocks, each of which will or will not change color, depending on the content of the urine. One of those is formulated to change color if there are elements present that indicate leukocytes in the urine.
If the leukocyte esterase shows a negative result, then the patient usually does not have an infection. There are some things that can cause the test to have a false negative, such as large amounts of vitamin C or protein in the urine. It is also possible to get a false positive due to a trichomonas infection or secretions from the vagina such as mucus or blood.
A positive leukocyte esterase typically indicates an infection, though it could also be some other sort of contamination. If the patient has other signs of a UTI, then treatment is often initiated for that condition without any further testing. In instances where the patient does not have symptoms of an infection, there may be need for a urine culture or examination of a sample under a microscope in order to make a diagnosis.
The results of the leukocyte esterase and the presence of symptoms combined can help a doctor to diagnose a urinary tract infection. These symptoms include a constant, urgent need to urinate, though the amounts produced are small, and a burning feeling while urinating. Urine may also look cloudy or have a pink hue due to the presence of blood. The urine may also have a strong smell. A urine infection can affect the urethra, bladder or kidneys.
Urinary tract infections are usually treated with oral antibiotics. If the infection is serious, hospitalization and intravenous (IV) administration of antibiotics may be required. Hospitalization is usually the result of an infection in the kidneys.