Leukocyte Esterase Urine Test
Leukocyte esterase (LE) is an esterase produced by white blood cells (WBCs) or leukocytes. A leukocyte esterase test is a urine test used to detect the presence of white blood cells and other health conditions associated with infection.
Normally, leukocyte esterase should not be present in the urine. However, when urinary tract and vaginal infections are present, white blood cells that contain this enzyme is often found in the urine. The leukocyte esterase test is also used to screen other infections, such as amniotic fluid infections and gonorrhea.
When the leukocyte esterase test is combined with the urinary nitrite test, it becomes an excellent screening test to establish a urinary tract infection (UTI). Urinalysis test strips, also called as urine dipsticks, can screen for both. A urine culture is required when a patient's urine sample shows a positive result for both leukocyte esterase and nitrite to identify what is causing the infection.
How is the test performed?
Before the test, you will be required to collect a clean urine sample. In males, the head of the penis must be cleaned, rinsed, and wiped before collection. The same goes for females in their urethral area. The ideal urine sample is collected using the clean-catch method, in which a small amount of urine is initially passed into the toilet bowl and then stopping the flow of urine to collect the midstream urine flow into a sterile cup until it is half full. After collecting the midstream urine, you can finish passing urine into the toilet.
Urine samples may also be collected using other methods, such as from a urinary catheter. If a patient has a urinary catheter, a healthcare worker may collect urine from the catheter for urine testing. However, if no catheter is present, a catheter may be temporarily inserted to collect a urine sample. The area will be first cleaned before catheter insertion into the urethra. Once inserted, urine will drain from the catheter into the urine container for the test. The catheter will be removed when enough amount of urine has been collected. When it comes to collecting urine samples from infants, a special sterile urinary bag may be used.
After the urine sample is properly collected, the test is immediately carried out. In this test, a urine dipstick is used. The presence of leukocytes is indicated by a change of color in the dipstick.
For this test, no special preparations are needed. The level of discomfort experienced when collecting urine usually depends on a number of factors, such as a person's sensitivity to pain. However, when a urine sample is collected from an existing urinary catheter, no pain is usually experienced. Patients may feel some discomfort if a temporary catheter is used to collect the urine sample.
Test results may vary and usually depend on a patient's medical history, gender, age, the method used for the test, and numerous other factors. The normal result in adults and children would be "negative" or "no color change" in the dipstick.
An abnormal result may indicate a urinary tract infection. However, there are also other factors that can turn the test abnormal without a urinary tract infection. They include:
- Trichomoniasis (a common sexually transmitted disease caused by a parasite called Trichomonas vaginalis)
- Heavy vaginal discharge (blood or mucus)
A false negative test can also be caused by the following conditions:
- High levels of vitamin C
- High levels of protein
What does the test indicate?
If the test result is positive and the white blood cell count in the patient's urine is high, then it may indicate a urinary tract infection, kidney infection, or kidney inflammation. A bacterial urinary tract infection is one of the common causes of leukocyturia. When a microscopic examination is done, leukocytes, bacteria, and erythrocytes are also visible.
The chemical test for nitrite will be positive when bacteria are present. A bacterial infection can be best indicated by a positive leukocyte esterase test. The presence of bacteria should also be further analyzed.
Dipsticks for the Chemical Analysis of Urine
A urine dipstick is a narrow plastic test strip that contains several chemical squares or pads in different colors. Each small chemical pad represents a specific component of the test that is used to interpret results. In this test, the test strip is dipped in the patient’s urine sample and color changes on each chemical pad are observed and noted. After dipping the test strip, changes in color usually take place after a few seconds to a few minutes. However, the results may become inaccurate if they are read too early or too long after dipping the test strip.
Combur-Test strips is a dry chemistry test used for the early detection of urinary tract infections (UTIs), kidney diseases, and diabetes. Aside from screening certain medical conditions, this test strip is also used for patient self-testing and monitoring of treatment. It is a test often used before the collected urine sample is microscopically analyzed and bacteriologically examined. The results are usually obtained within 60 seconds.
The advantages of using dipsticks are cost-effectiveness, convenience, and easy interpretation of results. By using dipsticks, results can be analyzed within minutes after urine collection. The test can also be done in the emergency room or doctor's office.
However, using dipsticks also has certain disadvantages, which include false-positive or false-negative results since dipstick tests are time-sensitive. Moreover, it is a qualitative test and not a quantitative test, which gives an accurate measurement of the quantity of abnormality.
The leukocyte esterase test is a part of a dipstick test that can screen urine samples of patients who often have genitourinary complaints. The test can be used in outpatient clinics, especially when microscopy is not readily available and when the patient's symptoms are unclear.
A urine sample that shows red blood cells, white blood cells, or bacteria is considered abnormal, and is often suggestive of the following conditions:
- Urinary tract infection
- Cystitis (urinary bladder infection)
- Pyelonephritis (kidney infection)
The combination of the urinary nitrite test and the leukocyte esterase test is usually an excellent test when it comes to screening urinary tract infections.