Generality
The urine nitrite test consists of immersing a test strip in a urine sample; after a few minutes, if significant concentrations of nitrites are found or not, the color of the paper changes according to the reference chromatic scale.
The concentration of these substances in the urine increases significantly in the presence of urinary infections, given the ability of many bacteria to convert urinary nitrates into nitrites (Escherichia Coli, Aerobacter, Proteus, Klebsielle, Pseudomonas, Enterococci, Staphylococci, etc.).
The urine nitrite test is more accurate if performed on the first urine of the morning, which has remained in the bladder for a long time, giving time to any bacteria to metabolize the nitrates. However, the negativity of the test does not exclude an infection, since some germs do not have the ability to reduce nitrates to nitrites. Furthermore, it is necessary that the urine coming from the kidney contains a significant amount of nitrates, mainly present in fresh vegetables and in many cured meats as preservatives (where nitrites are also often abundant). False negative results can also occur during antibiotic therapy or strong diuresis. To avoid false positive results it is instead important to discard the first urine emitted, collecting those of half of the flow in a clean test tube, naturally after having thoroughly washed your hands; women should also try to avoid possible contamination with vaginal secretions.
To improve the sensitivity and specificity of the test, the examination of nitrites in the urine is accompanied by the evaluation of the esterase activity of any urinary leukocytes. If both tests are positive, it is very likely the presence of a "urinary infection in progress; the diagnostic certainty will then be confirmed by the direct demonstration of leukocytes (white blood cells) at" microscopic examination. In this case, the microbiological examination (urine culture) will confirm the presence of bacteria and identify the species in question, while the antibiogram will evaluate the susceptibility of these microorganisms to various antibiotics.
The presence of a "urinary infection, as well as a positive nitrite test in the urine, is often signaled by symptoms such as frequent urge to urinate, pain or burning during urination, cloudy urine and a pungent odor, pain in the lower part abdomen in the kidneys, chills, fever, sweat and pains during intercourse.
What's this
Nitrites in the urine are the product of bacterial activity and are an indication of urinary tract infection (kidneys, ureters, urethra and bladder).
Because it is measured
Nitrites in the urine can indicate the presence of an "urinary infection in progress. Some bacteria have, in fact, the ability to metabolise nitrates into nitrites. Often, urinary infections are caused by intestinal bacteria such as Escherichia coli, Enterococci and Staphylococci.
Several symptoms can portend a "urinary infection:
- Repeated urge to urinate;
- Feeling of not having completely emptied the bladder
- Pain or discomfort when urinating
- Cloudy urine
- Pain in the lower abdomen.
Typically, a positive nitrite test will be accompanied by other tests to ascertain whether there is really an infection. For example, a "urinary infection is often signaled also by the presence of leukocytes in the urine, the defense cells of our organism.
Once the probability of an infectious process has been ascertained, it is recommended to perform a "urine culture, a microbiological examination that will allow us to understand which is the causal bacterial species.
Subsequently, an antibiogram will be done, in order to identify the most suitable antibiotic to counteract the microorganism.
In case of suspected urinary tract infection, it is necessary to contact a doctor, who will be able to advise and follow the patient in the different phases that will lead to the choice of the best therapy.
Normal values
Under normal conditions, the nitrite value in the urine should be zero.
The finding of small traces of urinary nitrites can be considered physiological, as it can depend on the diet. Nitrites are mainly present in fresh green leafy vegetables and in many cured meats as preservatives.
High Urine Nitrites - Causes
The concentration of nitrites in the urine increases in the presence of urinary tract infections.
There are different types of bacteria capable of transforming, by means of a reduction reaction, the nitrates into the nitrites found in the urine.
These microorganisms include:
- Escherichia coli: a bacterium that normally lives in the last section of our intestine and which can easily come into contact with the urethra, causing cystitis.
- Proteus spp.: bacteria typical of recurrent urinary tract infections of elderly and catheterized patients.
- Pseudomonas: bacterium found very often in human feces;
- Enterococci: bacteria responsible for urinary tract infections, among which we find Enterococcus faecalis a commensal of our intestine;
- Staphylococci: bacteria responsible for urogenital infections.
In other cases, the significant presence of nitrites can be traced back to a particularly unbalanced diet, which sees an excessive consumption of green leafy vegetables or sausages, which generally contain many preservatives.
The use of drugs such as antibiotics or diuretics and the intake of high amounts of vitamin C can also increase the concentration of nitrites in the urine.
Low Urine Nitrites - Causes
Barely noticeable amounts of nitrite in the urine can be considered normal. These substances are contained in many foods and are therefore eliminated with urine, tears and sweat.
Don't be alarmed, therefore, if small amounts of nitrite are found in a urine sample. The problem can arise if the quantity of the aforementioned substances is higher.
It should be noted, however, that negativity does not automatically exclude the presence of an "infection: there are infectious diseases caused by bacteria other than those mentioned that do not determine the finding of nitrites in the urine.
How it is measured
Nitrites in the urine can be easily detected by having a simple urinalysis.
The test is usually carried out in the morning, when the urine has had plenty of time to stay in the bladder, causing any bacteria that could be responsible for the transformation of nitrates into nitrites to act.
To perform the nitrite test, simply dip a test strip into the urine sample; after a few minutes, if significant concentrations of nitrites are found, the color of the paper will change according to the reference chromatic scale. In this case, the microscopic view of the urine sample should also show the presence of bacteria in the urine.
Preparation
For the evaluation of nitrites in the urine it is necessary to collect a small amount of urine in the morning, fasting, after having carried out an accurate intimate hygiene and after having let go of the very first emission (which may contain germs present outside the apparatus urinary).
In the case of women, it is good to carry out the examination away from the menstrual period.
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.
Taking certain medications (such as antibiotics and diuretics) or using vitamin C can increase the concentration of nitrites, so you will need to tell your doctor.
Interpretation of Results
A positive test for nitrites in the urine indicates a probable bacterial infection of the urinary tract.
In the event that urinalysis has shown the presence of nitrites in concentrations that are too high, it will be necessary to immediately submit the results to the doctor. To be sure that it is a "bacterial infection, it is necessary to be positive in several tests: nitrites in the urine, leukocyte esterase and urine culture to identify the causative agent."
In the case of urinary tract infections, the doctor will prescribe specific antibiotic-based therapies. Depending on the pathological agent involved, there will be a need to resort to a different type of antibiotic, after having appropriately identified it with an antibiogram. Using the wrong drug can cause delays in treating the infection, as well as predisposing to more serious problems.
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