Leukocyte esterase in urine: clinical significance and correct interpretation

Leukocyte esterase is a parameter commonly reported in urinalysis. Its positivity indicates the presence of leukocytes in the urine, which may reflect an inflammatory or infectious process involving the urinary tract.

It is a screening test, useful but not diagnostic, and must always be interpreted within the patient's clinical context.

What is leukocyte esterase?

Leukocyte esterase is an enzyme produced by white blood cells.
Its detection by urine dipstick indicates leukocyturia, that is, the migration of leukocytes into the urinary tract in response to an inflammatory stimulus.

Conditions in which it may be positive

A positive leukocyte esterase result may be associated with:

• urinary tract infections (cystitis, urethritis, pyelonephritis)

• prostatitis in men

• non-infectious inflammatory conditions

• contamination of the urine sample (improper collection)

It is therefore essential to correlate this finding with:

• the presence or absence of symptoms

• other urinalysis parameters (nitrites, bacteriuria, sediment)

• possible urine culture results

Positive leukocyte esterase in the absence of symptoms

In asymptomatic patients, an isolated finding of leukocyte esterase:

• does not automatically require treatment

• may indicate transient leukocyturia or an inadequate sample

• may justify repeating the test or performing a urine culture

Empirical use of antibiotics in the absence of clinical indications is discouraged.

When specialist evaluation is indicated

Medical consultation is recommended in the presence of:

• burning or pain during urination

• increased urinary frequency or urgency

• suprapubic, perineal, or lumbar pain

• fever or systemic signs

Clinical evaluation allows correct interpretation of the finding and, if necessary, the initiation of targeted therapy.

Conclusions

Leukocyte esterase represents a marker of possible inflammation, but it is not a diagnosis in itself.
Only a comprehensive clinical assessment can determine whether the finding is pathologically relevant and requires treatment.

Correct interpretation of laboratory tests is a key component of prevention and the protection of urinary health.