bpj-sce-august-2020

Interpretation of leukocyte esterase and nitrites on dipstick in females
Urine dipstick testing is not necessary to diagnose a
textbook UTI, but in practice it is often performed as the
presence or absence of leukocyte esterase and nitrites
can provide useful information, e.g. ruling out a UTI in a
patient with non-specific symptoms.
Leukocyte esterase is an enzyme released by
neutrophils and macrophages. A urine dipstick positive
for this enzyme indicates pyuria (an increased number
of leukocytes). UTIs are a common cause of pyuria and
haematuria, but also consider sexually transmitted
infections such as chlamydia. 26 The presence of leukocyte
esterase on dipstick may also be due to non-infectious
renal diseases such as glomerulonephritis. Contamination
of samples by vaginal secretions may cause a false-positive
result.
Nitrites are generally found in urine due to the
reduction of nitrates to nitrites by Gram-negative bacteria
such as Escherichia coli. The detection of bacteria in urine
by nitrite positive dipstick is also dependent on nitrates
from the patient’s diet (vegetables) and incubation time
in the bladder. Gram positive uropathogens such as
Staphylococcus saprophyticus and Enterococcus do not
produce nitrate reductase and the dipstick will be negative
for nitrites if the infection is due to these bacteria.
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52 Best Practice Journal – SCE Issue 1 www.bpac.org.nz