Leukocytes, commonly known as white blood cells, are integral components of the body’s immune system. A “positive leukocytes test” typically refers to the detection of an elevated number of these cells in a body fluid sample, most often urine. This finding, known as leukocyturia or pyuria, indicates that the body is actively mounting an inflammatory or infectious response that requires further investigation.
The Role of White Blood Cells
White blood cells are continuously produced in the bone marrow and circulate through the bloodstream and tissues, acting as surveillance for potential threats. Their fundamental function is to identify and neutralize foreign entities, such as bacteria, viruses, and fungi, and to clear away cellular debris from injured tissue. Leukocytes are a diverse group that includes five main types: neutrophils, lymphocytes, eosinophils, basophils, and monocytes. When the body detects an issue, these cells rush to the site of inflammation or infection. Neutrophils, the most numerous type, are usually the first responders, employing an enzyme called leukocyte esterase to destroy pathogens.
Interpreting the Positive Test Result
The positive result in a urine test is most often detected using a chemical dipstick that reacts to the presence of leukocyte esterase. A normal urine sample should contain very few white blood cells, generally fewer than five per high-power microscopic field. Any result exceeding this threshold indicates inflammation within the urinary tract or kidneys. The degree of positivity, often reported as trace, small, moderate, or large, generally correlates with the severity of the inflammatory reaction. A highly positive result suggests a robust immune response to a more significant issue, such as a full-blown bacterial infection. While a positive leukocyte esterase test strongly indicates the presence of white blood cells, it does not confirm the presence of bacteria, making it a screening tool rather than a final diagnosis. A key distinction is whether the test also shows nitrites. Nitrites are a byproduct of certain common bacteria, and their simultaneous presence makes a bacterial urinary tract infection highly probable.
Common Causes of Leukocyte Elevation
The most frequent cause of a positive leukocyte test in urine is an acute Urinary Tract Infection (UTI), where bacteria have colonized the urethra or bladder. The immune system recruits white blood cells to combat this bacterial invasion, which then exit the body through the urine. If the infection travels upward to the kidneys, a condition known as pyelonephritis, the leukocyte count will often be even higher and may be accompanied by systemic symptoms like fever and flank pain. Kidney stones can also trigger a positive result, causing obstruction and irritation that leads to localized inflammation. In men, inflammation of the prostate gland, or prostatitis, can result in leukocytes migrating into the urine. Less common causes include non-bacterial inflammatory conditions like Interstitial Cystitis or infections caused by organisms like Chlamydia or tuberculosis. These often present as “sterile pyuria,” meaning leukocytes are present but routine cultures show no bacteria.
Necessary Follow-Up and Treatment
A positive leukocyte test result is a signpost that necessitates further action, not a definitive diagnosis on its own. The next step is typically a microscopic examination of the urine sample to confirm the number of white blood cells and a urine culture. The culture is the gold standard for identifying the specific type of bacteria, if any, and determining which antibiotics will be most effective against the organism. Treatment depends entirely on the underlying cause confirmed by these follow-up tests. If a bacterial infection, such as a UTI, is identified, a course of targeted antibiotics will be prescribed to eliminate the pathogen. For non-infectious causes like kidney stones, the focus shifts to managing the obstruction or pain. Chronic conditions like interstitial cystitis require anti-inflammatory management. Consult with a healthcare provider for any positive result, especially if symptoms are present, to ensure the correct diagnosis is made and appropriate therapy is started promptly.