Generality
Leukocyte esterase is an enzyme found in most white blood cells .
Its activity is manifested at the level of the proteins of the connective matrix, which the enzyme is able to degrade, contributing to the destruction of bacteria and foreign cells.
If large amounts of leukocyte esterase are found in the urine, it means that there are high concentrations of leukocytes in the urine; this indicates a probable urinary tract infection .
What's this
The esterase has the function of degrading the proteins that support the connective matrix.
Why do you measure
The leukocyte esterase test is a test that detects the presence of the enzyme in the urine. This finding indicates a probable urinary tract infection (urethra, urinary bladder, renal pelvis or kidney).
Leukocyte esterase is strongly correlated to the presence of white blood cells (leukocytes) in the urine.
This analysis is especially useful when it is necessary to distinguish between an asymptomatic bacteriuria and a urinary tract infection (IVU).
Associated examinations
To improve the reliability of the test and proceed towards a certain diagnosis, the leukocyte esterase examination is often accompanied by the evaluation of urinary nitrite, produced by bacterial activity.
The combination of these analyzes provides excellent screening to identify the presence of a urinary tract infection (UTI). Further confirmation is provided by the microscopic analysis of the urinary sediment, to also highlight the presence of leukocytes and / or bacteria in the urine.
Usually, once there is a positive test for the presence of the enzyme in the urine, another test is performed, the urine culture with antibiogram, to verify the extent and type of urinary infection in place.
Possible symptoms
The symptoms associated with leukocyte esterase in the urine may be non-specific and common to a large number of disorders and / or diseases. In general, however, a high level of this enzyme may be related to typical manifestations of urinary infections, such as:
- Sense of general malaise;
- Repeated urge to urinate;
- Feeling of not having completely emptied the bladder;
- Pain or discomfort during urination;
- Turbid and foul-smelling urine;
- Pain in the lower part of the abdomen.
When the exam is requested
The test to evaluate leukocyte esterase is required when the presence of a urinary tract infection responsible for discomfort and pain during urination, the frequent need to urinate or for all the other symptoms mentioned above is suspected.
Normal values
The leukocyte esterase test must give a negative result, therefore the average reference values must be zero.
High Leukocyte Esterase - Causes
In most cases, high leukocyte esterase indicates the presence of a urinary infection and / or inflammation.
More specifically, high levels of this enzyme can be caused by:
- Cystitis (very annoying inflammation that affects the bladder mucosa);
- Kidney stones (small aggregations of mineral salts, which, forming in the urinary tract, favor the onset of infections);
- Polycystic kidney disease (genetic pathological condition in which cysts form on renal tissue);
- Acute or chronic urethritis (inflammation of the urethra);
- Prostatitis (inflammation of the prostate gland);
- Pregnancy;
- Bladder cancer.
Low Leukocyte Esterase - Causes
The leukocyte esterase test should be negative, so that it signals a normal course of our body.
Its negativity indicates, in fact, "the absence of the enzyme".
How to measure it
The leukocyte esterase test is quick and easy to perform. The examination is performed on a urine sample, normally collected in the morning, on an empty stomach.
To perform the leukocyte esterase test, simply immerse a test strip in the urinary specimen. After a few minutes, if significant quantities of leukocyte esterase are found, the color of the map will change according to the reference chromatic scale, acquiring more and more intense shades based on the concentration levels of the enzyme.
In the event of a positive outcome, the urine specimen is normally viewed under the microscope, which should show the presence of leukocytes and / or bacteria.
Preparation
The leukocyte esterase test does not require any special preparation; it is simply necessary for the patient to urinate normally, collecting a sample of the intermediate mite (that is, after letting go of the very first emission of urine, which may contain the germs present outside the urinary tract).
The urine must be collected in a sterile container, which must be carefully closed immediately afterwards and taken to the laboratory within a short period of time.
Factors influencing the exam
Some conditions may result in a false positive test result for leukocyte esterase:
- Infection with Trichomonas vaginalis ;
- Vaginal secretions (blood or major mucus losses).
Other situations can lead, instead, to a false negative result:
- Use of antibiotics, such as tetracycline;
- High amounts of ascorbic acid (vitamin C), boron and oxalic acid in the urine.
Interpretation of Results
Normally, few white blood cells are present in the urine and the leukocyte esterase examination gives a negative result. When the number of leukocytes increases significantly, the enzyme test becomes positive.
A high value of leukocyte esterase is likely to indicate the presence of a urinary tract infection .
In the latter case, further investigations will be needed to establish the cause of the phenomenon.
Furthermore, if the test reveals a high presence of squamous epithelial cells, the possibility exists that the sample has been contaminated, so for a precise diagnosis it will be necessary to repeat the test.
