Generality
The urine nitrite test consists of immersing a reactive strip in a urinary sample; after a few minutes, if significant concentrations of nitrites are found or not, the color of the map varies according to the reference color scale.
The concentration of these substances in the urine increases significantly in the presence of urinary infections, given the ability to convert urinary nitrates into nitrites, typical of many bacteria (Escherichia Coli, Aerobacter, Proteus, Klebsielle, Pseudomonas, Enterococci, Staphylococci, etc.).
The nitrites test in urine is more accurate if performed on the first morning urine, which stopped for a long time in the bladder giving time to any bacteria to metabolize the nitrates. The negativity of the test does not however exclude an infection, given that some germs do not have the ability to reduce nitrates to nitrites. Furthermore, it is necessary that the urine coming from the kidney contain a significant amount of nitrates, present above all in fresh vegetables and in many salamis as preservatives (where nitrites often abound). False negative results may 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 the 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, the presence of an ongoing urinary infection is very likely; the diagnostic certainty will then be confirmed by the direct demonstration of leukocytes (white blood cells) on 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 the various antibiotics.
The presence of a urinary infection, as well as from the positivity to the examination of nitrites in the urine, is often signaled by symptoms as frequent urge to urinate, pain or burning during urination, cloudy urine and pungent odor, pains in the lower part of the abdomen with kidneys, chills, fever, sweat and pain during intercourse.
What's this
Nitrites in the urine are the product of bacterial activity and are an indication of infection of the urinary tract (kidneys, ureters, urethra and bladder).
Why do you measure
Nitrites in the urine may indicate the presence of an ongoing urinary infection . Indeed, some bacteria have the ability to metabolize nitrates into nitrites. Often, urinary infections are caused by intestinal bacteria such as Escherichia coli, Enterococci and Staphylococci.
Several symptoms may indicate a urinary infection:
- Repeated urge to urinate;
- Feeling of not having completely emptied the bladder;
- Pain or discomfort during urination;
- Turbine urine;
- Pain in the lower part of the abdomen.
Typically, a positive nitrite test will be supplemented with other tests to see if there is actually an ongoing infection. For example, a urinary infection is often also signaled by the urinary presence of leukocytes, defense cells of our body.
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, so as to identify the most suitable antibiotic to counteract the microorganism.
In case of suspected urinary tract infection, it is necessary to consult 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 value of nitrites in the urine must be zero.
The finding of small traces of urinary nitrite can be considered physiological, as it may depend on the diet. Nitrites are present mainly in fresh green leafy vegetables and in many cured meats as preservatives.
Nitrite in urine High - Causes
The concentration of nitrite in the urine increases in the presence of urinary tract infections.
There are different types of bacteria capable of transforming, through a reduction reaction, the nitrates in the nitrites that are found in the urine.
These microorganisms include:
- Escherichia coli : a bacterium that normally lives at the level of the last section of our intestine and that can easily come into contact with the urethra, causing cystitis.
- Proteus spp. : bacteria typical of recurrent infections of the urinary tract of elderly and catheterized patients.
- Pseudomonas : bacterium that is found very often in human feces;
- Enterococci: bacteria responsible for urinary tract infections, among which we find the 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 excessive consumption of green leafy vegetables or sausages, which generally contain many preservatives within them.
The use of drugs such as antibiotics or diuretics and the intake of high amounts of vitamin C can also increase the concentration of nitrite in the urine.
Nitrite in urine Low - Causes
Barely perceptible amounts of nitrites in the urine can be considered normal. These substances are contained in many foods and are therefore eliminated with urine, tears and sweat.
Therefore, do not be alarmed if small amounts of nitrites are found in a urinary sample. The problem may arise if the quantity of the aforementioned substances were 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 detection of nitrites in the urine.
How to measure it
Nitrites in the urine can be easily detected by undergoing a simple urine test.
The examination should be carried out, as a rule, in the morning, when the urine has had plenty of time to stand 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 immerse a test strip in the urine sample; after a few minutes, if significant concentrations of nitrites are found, the color of the map will change according to the reference color 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, on an empty stomach, after having carried out thorough personal hygiene and having let go of the very first emission (which may contain the germs present outside the apparatus urinary).
In the case of women, it is good to take the exam 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 some medications (such as antibiotics and diuretics) or using vitamin C can increase the concentration of nitrite, so you will need to tell your doctor.
Interpretation of Results
The positive test for nitrite detection in urine indicates a probable bacterial infection of the urinary tract.
In the event that urine tests have 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 have multiple tests: nitrite in the urine, leukocyte esterase and urine culture to identify the causative agent.
In the case of urinary tract infections, the doctor will prescribe therapies based on specific antibiotics. 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 medication can cause delays in treating the infection, as well as predispose to problems of a greater scale.
