Guide to Leukocyte Esterase

WRITTEN BY

The Levels Team

Updated: 05/22/2025|12 min read

Summary

Leukocyte esterase is an enzyme produced by white blood cells (leukocytes) that can be detected in urine during laboratory testing. Its presence serves as a marker for potential inflammation or infection in the urinary tract and is commonly used as a screening tool for urinary tract infections (UTIs).

Why It Matters

When the urinary tract is inflamed or infected, white blood cells are recruited to the area as part of the immune response. These cells release leukocyte esterase, which can then be detected during urinalysis.

A positive leukocyte esterase test may indicate:

• Urinary tract infections (common cause)
• Kidney inflammation (nephritis)
• Bladder inflammation (cystitis)
• Inflammation of the urethra (urethritis)
• Certain sexually transmitted infections that affect the urinary tract

It's important to note that leukocyte esterase testing is a screening tool rather than a definitive diagnostic test. A positive result suggests the presence of white blood cells (pyuria) but doesn't identify a specific cause. Confirmatory testing, such as urine culture, is typically needed to identify the specific microorganism causing an infection and to determine appropriate treatment.

Clinical Ranges

Lab Reference Range: Negative

Symptoms of Conditions Associated with Leukocyte Esterase

While leukocyte esterase itself is a laboratory finding and doesn't directly cause symptoms, the underlying conditions it may indicate (particularly UTIs) can present with:

• Frequent urination (can occur with bladder infections)
• Burning or pain during urination (dysuria, can occur with UTIs)
• Cloudy or strong-smelling urine (may be due to the presence of bacteria and white blood cells)
• Lower abdominal pain or pressure (may indicate bladder or kidney involvement)
• Lower back pain (can be associated with kidney infection, pyelonephritis)
• Fever (can occur with more severe infections like pyelonephritis)
• Blood in urine (can occur with significant inflammation or infection in the bladder or kidneys)
• General fatigue (can occur with many infections)

Lifestyle Factors That Can Impact It

Activities that may have a positive effect on leukocyte esterase include:

• Fluid intake: Drinking enough fluids throughout the day helps flush bacteria from the urinary tract, potentially reducing the risk of infections that would cause elevated leukocyte esterase.
• Diet choices: Certain foods and beverages (like cranberries and probiotics) may help prevent UTIs, while others (like excessive caffeine or alcohol) might irritate the urinary tract.
• Exercise: Regular physical activity supports immune function and overall health.

Other habits can negatively affect levels, such as:

• Personal hygiene: Poor hygiene practices can introduce bacteria to the urinary tract. Proper wiping technique (front to back), regular cleaning, and wearing breathable cotton underwear can help prevent bacterial growth.
• Sexual activity: Frequent sexual activity can increase the risk of UTIs, especially in women. Urinating before and after sexual activity can help reduce bacterial transfer.

Other Factors That Can Impact It

Genetic Conditions

• Certain genetic factors can make people more susceptible to UTIs and other conditions affecting leukocyte esterase levels.

Medical Conditions

• Diabetes: Elevated blood sugar creates an environment conducive to bacterial growth, potentially increasing UTI risk.
• Kidney disease: Impaired kidney function can affect immune response and increase susceptibility to infections.
• Autoimmune disorders: These conditions can cause inflammation throughout the body, including the urinary tract.
• Structural abnormalities: Physical variations in the urinary tract can make infections more likely.

Medications and Supplements

• Antibiotics: Can affect bacterial presence and immune response
• Immunosuppressants: May reduce white blood cell activity
• Vitamin C: High doses can affect test results
• Anti-inflammatory medications: May impact inflammatory response

Individual Factors

• Age: Older adults have an increased risk of UTIs
• Gender: Women have a shorter urethra, potentially increasing infection risk
• Pregnancy: Hormonal changes and physical pressure on the bladder can increase UTI risk
• Menopause: Hormonal changes affecting urinary tract health

Testing Accuracy and Stability

Factors That Can Affect the Accuracy of Your Test

• Ensuring a "clean catch" (wipe front to back, get sample midstream)
• Certain medications, including antibiotics (especially cephalosporins and tetracyclines) can cause false-positive or false-negative results
• Contamination from skin flora
• High-dose vitamin C (ascorbic acid) can cause false-negative results
• Dehydration concentrates urine and can lead to a false impression of the presence of an infection

How it Relates to Other Markers

Your healthcare providers may use other tests alongside leukocyte esterase to help determine the underlying condition:

• Urine culture: Identifies specific microorganisms potentially causing infection and determines the most effective antibiotic treatment.
• Nitrite test: Often performed alongside leukocyte esterase, this test helps detect bacteria that convert nitrates to nitrites. Combining both tests may increase screening accuracy.
• Complete blood count: Helps evaluate systemic infection and immune response. This can help determine if the infection has spread beyond the urinary tract.

What Results May Mean in the Context of Other Markers

• Positive leukocyte esterase with positive nitrite and positive urine culture: May suggest a bacterial urinary tract infection

Follow-up Considerations

If leukocyte esterase is detected in your urine, your provider may recommend certain follow-up actions. You should always speak to your doctor if you have medical questions or before making medical decisions.

When Re-Testing May be Appropriate

• May re-test immediately if contamination is suspected
• After completing antibiotic treatment
• If symptoms persist despite treatment
• Regular monitoring for chronic conditions
• During pregnancy check-ups

Additional Testing Your Doctor May Consider

• Kidney function tests
• Sexually transmitted infection (STI) screening
• Prostate-specific antigen (for men)
• Diabetes screening

When Additional Care May be Warranted

• Fever over 101°F (38.3°C)
• Severe pain or discomfort
• Blood in urine
• Symptoms lasting more than 3 days despite treatment
• Recurring infections
• During pregnancy

Bibliography