Urinalysis - The Carter Center

80
4.9 Determination of Nitrite
Introduction
Tests for nitrite was not a part of the routine urinalysis. It is included
recently on commercial multiple-reagent strips such as Combur 9 and N-
Multistix. The detection of nitrite in the urine can be used to indicate the
presence of bacteria such as Escherchi coli, proteius, klebsiella,
enterobacter, citrobacter, and salmonella will reduce urinary nitrate to
nitrite.The presence of urinary nitrite(in urine sample collected under
sterile condition) indicates the existence of a urinary tract infection.
Detection of such infections is particularly important in pregnant women
and young girls to prevent permanent renal damage. Since the detection
rate increases when the urine is held in the bladder for at least 4-6
hours, test for nitrite must be performed on the first morning urine
specimen. For proper detection of nitrite the patient diet must also
contain enough reducible nitrate on which the bacteria can act.
Types of Method Used for Detection of Nitrite
There are two methods that are used to detect bacteria in the urine
during routine urinalysis.
1. Microscopic examination: urine sediment when examined
microscopically can reveal bacteria when present. If the sample is
collected under sterile condition.
2. Chemical dipstick method for nitrite can also give clue.
The nitrite area in the multiple reagent strip is calibrated so that any
shade of pink color that develops within 30 sec indicates an amount of
nitrite produced by 105 or more organisms per milliliter in the urine
specimen.
A positive result from the nitrite test is a reliable indication of significant
bacteriuria ( the presence of bacteria in the urine) and is an indication