A urinalysis is a common diagnostic test that examines a urine sample to help detect a range of health conditions. This comprehensive analysis evaluates the physical, chemical, and microscopic properties of urine. One specific component often assessed in a urinalysis is WBC esterase, an enzyme present in certain white blood cells. Its detection in urine can provide important clues about the presence of inflammation or infection within the urinary tract.
Understanding WBC Esterase
WBC esterase is an enzyme released by white blood cells, particularly neutrophils, which are a type of leukocyte. Neutrophils are a primary defense against bacterial infections and inflammation. When these white blood cells are present in the urine, often due to inflammation or infection, they release WBC esterase. This enzyme serves as a marker for leukocyturia, indicating white blood cells in the urine.
The test for WBC esterase is performed using a urine dipstick. This strip has a color-sensitive pad that reacts to the enzyme. When immersed in a urine sample, the esterase enzyme, if present, catalyzes a chemical reaction resulting in a color change on the pad. The intensity of the color change is proportional to the amount of WBC esterase, indirectly indicating the concentration of white blood cells in the urine. This method offers a rapid way to screen for white blood cells in the urinary system.
Interpreting Your Urinalysis Results
A positive WBC esterase result indicates the presence of white blood cells in the urine, a condition known as pyuria. This finding suggests inflammation or infection within the urinary tract, such as a urinary tract infection (UTI) or a kidney infection. While a positive result raises suspicion, WBC esterase is a screening tool and not a definitive diagnosis on its own.
Conversely, a negative WBC esterase result means that no significant inflammation or infection is detected. However, a negative result does not rule out an infection, as certain factors can interfere with the test, such as high levels of protein or vitamin C in the urine. The WBC esterase test is evaluated alongside other urinalysis findings, particularly nitrites. Nitrites are produced by certain bacteria commonly associated with UTIs, and a positive result for both WBC esterase and nitrites increases the likelihood of a bacterial infection.
Next Steps After a Positive Test
If your urinalysis shows a positive WBC esterase result, further investigation is warranted. A positive result indicates the presence of white blood cells but does not identify the specific cause or type of infection. Healthcare providers recommend additional tests to identify the cause.
Follow-up procedures include a microscopic examination of the urine sample. This allows visualization and counting of white blood cells, red blood cells, and bacteria present in the urine. A urine culture is also performed, where a urine sample is sent to a laboratory to grow and identify any bacteria or fungi. A urine culture can determine the specific microorganism causing an infection and help guide antibiotic treatment. Consult with a healthcare professional to discuss your results and determine the appropriate diagnostic and treatment plan.