NITRITE
Detection of nitrite in urine, coupled with leukocyte
esterase, is a rapid method for detecting asymptomatic urinary tract infection.
Some bacteria such as Escherichia coli, can convert urinary nitrate into
nitrite. Urine must be retained in the bladder for at least 4 hours for this
conversion to occur. The first morning specimen is ideal for the test. The
intensity of the colour produced is related to the amount of nitrates in urine;
and not to the number of bacteria.
Reagent Strip Tests
Principle Nitrite reacts with an aromatic amine such as
sulphanilic acid or arsanilic acid in an acid medium to form a diazonium salt.
This salt is then reacted with another aromatic ring such as quinolin to give a
pink or red colour. A false negative reaction may occur. Multistix strips The
reagents used in this strip are p-arsanilic acid and 1, 2, 3, 4-tetrahydro
benzo-(h)-quinolin-3-01. It can detect 0.06 - Img/ dl nitrite in urine.
Chemstrip
strips This strip contains sulphanilamide and
3-hydroxy-1,2,3,4-tetrahydro-7,8benzoquinoline. It can detect 0.05 mg/dl
nitrite in most specimens.
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