NIT (bacteriuria) with a urine analyzer

Norma
Negative

Šlapimo indas

NIT indicator shows bacteriuria. In a healthy person’s urine, the NIT indicator is always negative. When consuming foods rich in nitrites, the urine NIT indicator is never positive unless there is a urogenital infection. If treated with medications containing a lot of nitrites, the NIT indicator is also never positive. The presence of nitrites in the urine is related to bacterial reduction of nitrates. Normal human diet ensures an adequate amount of nitrates, which bacteria in the urinary tract convert to nitrites. In some cases (during fasting, parenteral nutrition), there may not be enough nitrates for a sufficient amount of nitrites to form, and in the presence of a urogenital infection, they can be detected in the urine NIT test. In the case of bacteriuria, the NIT test can sometimes be falsely negative. These conditions include: 1) very intense diuresis; 2) parenteral nutrition; 3) a diet completely devoid of plant-based products, fasting; 4) a long time interval before the start of the examination (in over 4 hours, the NIT indicator in unexamined urine can significantly decrease).

By performing a random test with the NIT indicator, it is possible to detect approximately 50% of all cases of bacteriuria. This indicator can be increased to 90% if several rules are followed: 1) repeat morning urine tests (it is important to know that bacteria in the urinary tract need at least 4-6 hours to produce nitrates; therefore, morning urine, if there is no very pronounced nocturia, is most suitable); 2) warn the patient the day before the test to consume a normal amount of vegetables and plant-based food; 3) refrain from antibacterial treatment for at least three to four days before the test.

Sometimes, even in the absence of bacteriuria, the NIT test can be falsely positive: 1) bacteria can enter from the surface of the container and start multiplying if the urine is left standing for a long time; 2) the patient is being treated with medications containing impurities of phenazopyridine.

Almost all known causative agents of urinary tract infections can be detected by the NIT indicator (E. coli, Klebsiella, Aerobacter, Citrobacter, Salmonella, Staphylococcus, Pseudomonas, etc.). Urinary tract infection is the second most common (after respiratory tract infections) cause of bacterial infections in humans. Failure to detect bacteriuria in time can lead to complications such as chronic pyelonephritis, renal insufficiency, uremia.

Source | Handbook of Basic Laboratory Tests | Doctor of Medical Sciences Gintaras Zaleskis