Journal of Community Nursing - page 90

90 JCN
2013,Vol 27, No 4
CONTINENCE
Blood (erythrocytes)
Protein.
Testing for nitrites and leucocytes
works on the rationale that bacteria
present in the urine cause urinary
nitrates to breakdown into nitrites.
Similarly, a higher concentration of
the leucocyte esterase enzyme will
be present in the urine as a result of
the increased neutrophils present
during infection (Balakrishnan and
Hill, 2011).
Urine dipstick testing for nitrites
and leucocytes is most effective
when the bacterial count is high,
however, diagnosis is more accurate
if used in combination with other
tests (
BMJ Best Practice, 2013
). If
the dipstick result is negative, but
the symptoms suggest a UTI, the
probability of a UTI is still relatively
high (
BMJ Best Practice, 2013
).
Microbiology testing
Microscopy can be used to detect
haematuria, pyuria (white cells in the
urine) or bacteriuria (Balakrishnan
and Hill, 2011), or to confirm the
organism type and guide antibiotic
selection in complicated UTI
or
pyelonephritis (kidney infection)
(
BMJ Best Practice
, 2013). A UTI
might be considered complicated if
there are risk factors that predispose
the patient to infection (e.g. urinary
obstruction or vesico-ureteric reflux).
Urine culture and sensitivity
testing is the most specific and
sensitive test for confirmation of a
UTI. A midstream urine sample can
be sent for cultures and sensitivity
analysis to confirm the diagnosis
and to ensure that an appropriate
antibiotic can be prescribed (SIGN,
2012). A mid-stream urine sample
should be taken for culture to
ensure that contamination of the
sample is kept to a minimum
(Mahaffey, 2006).
There are limitations to both
near-patient testing and laboratory
microbiology. The detection of
protein and blood in the urine by
dipstick testing is unreliable, with
a high rate of false positives and
false negatives, and is, therefore, of
comparatively little diagnostic value
(Balakrishnan and Hill, 2011).
Similarly, urine dipstick testing
in general has been found to be
unreliable in the following groups
(Balakrishnan and Hill, 2011):
Pregnant women
Children under three years of age
Patients whose urinary tracts have
structural anomalies
Patients with diabetes mellitus
Patients who are
immunocompromised.
Therefore, urine dipstick testing is
of little use in these patient groups.
With mid-stream urine samples,
it may not always be possible
to eradicate all contamination.
Specimens need to be either
processed promptly or refrigerated
after collection in order to minimise
bacterial multiplication (Balakrishnan
and Hill, 2011).
Figure 1
illustrates a
protocol for diagnosis of UTI.
CAUSATIVE ORGANISMS
At the current time,
Escherichia coli
species are the most common cause
of UTI (in 70–95% of uncomplicated
cases). Other causative pathogens
in uncomplicated UTIs include
Enterobacteriae such as
Proteus
mirabilis
and
Klebsiella
species,
Figure 1.
Protocol for diagnosis of UTI (adapted from Health Protection Agency [2010a]).
Mild or
2 symptoms of UTI
Obtain urine sample
Urine cloudy – dipstick test
Urine not cloudy
Severe or
≥ 3 symptoms of UTI
Give empirical
antibiotic treatment
Negative nitrite,
leucocytes and blood or
negative nitrite
and leucocyte and
positive blood
or protein
Positive nitrite,
leucocytes and blood
or positive nitrites
alone
Negative nitrite and
positive leucocyte
Could equally be UTI
or other diagnosis.
Treat if severe
symptoms or consider
delayed antibiotic
treatment and urine
culture
Probable UTI
Treat with first-line
agents (follow HPA
guidance)
Consider other
diagnosis
Consider other
diagnosis
Patient presents with UTI symptoms
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