What Is Urine Leukocyte Esterase Test? (2024)


Urinalysis is extremely useful in diagnosing urologic disorders such as calculi, urinary tract infections (UTIs), and cancer. It can also alert a physician to systemic illness affecting the kidneys. Urinalysis is not suggested as a routine screening method except in pregnant women. Urinary tract infections are classified as urethra, bladder, ureters, or kidneys caused by non-commensal microorganisms such as Escherichia coli, Staphylococcus saprophyticus, and Enterococcus faecalis. Enterobacteriaceae species. (mostly Proteus mirabilis and Klebsiella species), group B streptococci, Pseudomonas aeruginosa, and Citrobacter sp. are other uropathogens. They are commonly caused by uropathogens in fecal flora infiltrating the urethra and ascending into the bladder through the urethra. Pyelonephritis is caused by uropathogenic migrating from the bladder into the kidneys through the ureters.

How Are Urinary Tract Infections Classified?

Urinary tract infections (UTIs) are classified as either complicated or uncomplicated:

1. Uncomplicated UTIs: These are further characterized as cystitis (lower urinary tract) and pyelonephritis (upper urinary tract).

  • Cystitis is characterized by dysuria, frequency, urgency, haematuria (blood in the urine), and suprapubic discomfort.
  • Pyelonephritis is characterized by flank pain, costovertebral angle stiffness, fever, nausea, vomiting, and urinary symptoms.

Children frequently come with unusual symptoms such as stomach discomfort, vomiting, fever, and irritability, and rarely with urinary tract symptoms.

In children, UTIs can lead to significant complications such as renal scarring and end-stage kidney failure. Uncomplicated UTIs arise in generally healthy people with no anatomical or neurological urinary tract problems. Female gender, past UTI, sexual activity, vagin*l infection, diabetes, obesity, and genetic susceptibility are all risk factors.

2. Complicated UTIs: They arise when the host defense or urinary tract or host defense is compromised due to the obstruction of the urinary tract, retention of urine caused by neurological disease, immunosuppression (such as diabetes), renal failure, kidney transplant, pregnancy, or the presence of foreign bodies such as calculi, intraoperative catheters, or other drainage devices. Recurrent UTIs, perinephric abscesses, kidney failure, urosepsis, and mortality are most common in these individuals.

What Is Urine Leukocyte Esterase Test?

A urine leukocyte esterase test is a dip test to evaluate the presence of white blood cells and other urine infection indicators. This indicates that the patient is suffering from a urinary tract infection. If this test results in a positive result, the urine should be examined under a microscope for white blood cells and other signs of infection. Previous studies demonstrated that the sensitivity of the leukocyte esterase test (LET) ranged from 45 to 100 percent for detecting urogenital CT infections in males, with specificity ranging from 78 percent to 96 percent. Compared to the nucleic acid amplification test (NAAT) results for Neisseria gonorrhoeae (NG) and Chlamydia trachomatis (CT) detection, LET alone demonstrated sensitivities of 66.7 percent and 60 percent, respectively, and specificities of 90.7 percent and 94.7 percent. The urine leukocyte esterase test is otherwise called the WBC esterase test. The test result is negative for the urine leukocyte esterase test, which suggests that the color of the dipstick changes, suggesting the presence of the host’s polymorphonuclear cells.

Why Do Leukocytes Appear in Urine?

Increased leukocyte levels in urine may indicate urinary tract infections, tumors in the pelvic region, obstruction of the urinary bladder and urinary tract, and kidney stones and infection. Some medications like steroids, proton pump inhibitors, and nonsteroidal anti-inflammatory drugs may also cause increased leukocyte levels in urine.

Why Is Leukocyte Esterase Test (LET) Performed?

The leukocyte esterase test (LET) is important in normal urine analysis. This non-specific, quick dipstick assay detects the presence of an esterase enzyme in urine generated by polymorphonuclear leukocytes (white blood cells).

The urine test is an important preliminary evaluation used to diagnose various disorders. Detecting leukocyte esterase during a normal urine examination is sensitive and specific for identifying urinary tract infections.

The leukocyte esterase test (LET) can also screen for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) infections.

How to Perform the Urine Leukocyte Esterase Test?

A clean catch (midstream sample) urine sample is recommended. The clean-catch procedure eliminates pathogens from entering a urine sample from the penis or vagin*. The doctor may offer patients a special clean-catch kit with a washing solution and sterile wipes to collect urine. Follow the directions properly to make sure that the results are correct.

Urine samples are examined immediately after they are collected. The service provider utilizes a dipstick with a color-sensitive pad. If there are white blood cells in the urine, the color of the dipstick changes to alert the clinician.

What Does Abnormal Value Suggest?

An abnormal result suggests the presence of a urinary tract infection. Even if the patients do not have a urinary tract infection, the following factors could result in an abnormal test result:

  • Infection with Trichom*onas (such as trichom*oniasis).

  • Infection with Chlamydia trachomatis (CT), Neisseria gonorrhoeae (NG), Trichom*onas vagin*lis, and Mycoplasma genitalium are the natural causative organisms of sexually transmitted diseases.

  • Secretions from the vagin*l cavity (such as blood or heavy mucus discharge). Mucus in urine may also cause increased leukocyte count in urine.

The following factors may interfere with a favorable result if the patients have a urinary tract infection.

  • High protein levels and vitamin C levels are high in the urine.

What Are the Advantages and Drawbacks of the Dipstick Method?

The existence of bacteriuria alone does not indicate urinary tract infection. The decreased sensitivity of urine dipstick tests in detecting lower colony counts hinders their value in identifying simple urinary tract infections in women.

This technique would save the laboratory significant time and money, and roughly one out of every five women with urinary tract infection symptoms and positive urine cultures would be undetected.


Leukocyte esterase is a specific white blood cell (white blood cell) protein. A leukocyte esterase test can quickly determine if there are too many white blood cells in the urine. A leukocyte esterase test detects intact or broken white blood cells. A positive urinary leukocyte esterase test indicates either infection of the lower urinary tract (bladder and urethra) or contamination of the sample. LET detection is a straightforward and low-cost diagnostic test widely available in human immunodeficiency virus (HIV) and sexually transmitted infections (STI) clinics. LET is not a diagnostic test for CT or NG infection. However, it has a comparably high negative predictive value (NPV) for CT and NG infection. In low- and middle-income countries, LET might be useful in identifying CT and NG infections.

What Is Urine Leukocyte Esterase Test? (2024)
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