A urinalysis is a routine test used to examine the physical, chemical, and microscopic properties of urine, providing a window into the health of the urinary tract and kidneys. This test often includes a check for the presence of white blood cells, also known as leukocytes. When a lab report returns a result of “1+ leukocytes,” it indicates a low, yet measurable, level of these immune cells in the urine sample. Understanding this specific finding requires placing the result within the context of the testing method and the body’s normal biological processes.
Understanding Leukocytes and Pyuria
Leukocytes are immune system cells responsible for defending the body against foreign invaders or responding to irritation and inflammation. Their presence in the urine is a response to a perceived problem somewhere along the urinary tract, which includes the kidneys, ureters, bladder, and urethra. Under normal, healthy conditions, the urine should contain very few or no leukocytes, as the urinary tract is designed to be a sterile environment.
The medical term for an elevated number of white blood cells in the urine is pyuria. In microscopic analysis, pyuria is defined as finding more than three to ten white blood cells per high-powered field (WBC/HPF). The “1+” result, however, usually comes from a dipstick test, which detects an enzyme called leukocyte esterase, found inside certain white blood cells.
The dipstick test provides a quick, semi-quantitative reading reported as negative, trace, 1+, 2+, or 3+. Because the dipstick detects the enzyme, it is a screening tool that suggests the possibility of inflammation or infection. A result of 1+ suggests a mild presence of these immune cells, falling just above a completely negative finding.
Interpreting the 1+ Result
A 1+ leukocyte finding is considered a low-level or borderline result that must be interpreted carefully alongside a person’s symptoms and other urinalysis markers. This finding alone, especially without symptoms like pain during urination or increased urgency, often does not signify a serious infection. Transient, non-disease causes can easily produce a mild elevation in leukocyte esterase.
The most common reason for a 1+ reading is contamination during the sample collection process, particularly in female patients. If a proper midstream, clean-catch technique is not used, white blood cells from the genital area can mix with the urine, leading to a false-positive result. Minor irritation from recent sexual activity, strenuous exercise, or slight dehydration can also temporarily increase urinary leukocytes.
If the dipstick shows 1+ leukocytes but is negative for nitrites and blood, the result is less concerning for a classic bacterial urinary tract infection (UTI). Nitrites are a chemical byproduct of certain bacteria, and their presence strongly suggests an active bacterial infection. An isolated 1+ leukocyte finding suggests inflammation or an early immune response that may resolve on its own.
Primary Causes of Leukocyte Elevation
While a 1+ reading can be incidental, a persistent or higher elevation of leukocytes (2+ or 3+) points toward a true condition causing inflammation in the urinary system. The most frequent cause of significant pyuria is a bacterial urinary tract infection (UTI) affecting the bladder or urethra. The immune system mobilizes large numbers of leukocytes to the site of infection to fight the invading bacteria.
If the infection is more severe, such as pyelonephritis (a kidney infection), leukocyte counts will be substantially higher. Inflammation from non-infectious sources can also cause pyuria, a condition referred to as sterile pyuria when no bacteria are detected in a culture. Kidney stones, for example, can cause irritation and obstruction, leading to a localized inflammatory reaction.
Causes of Sterile Pyuria
Certain medications, such as some nonsteroidal anti-inflammatory drugs (NSAIDs) or specific antibiotics, can cause kidney inflammation called interstitial nephritis, resulting in pyuria. Other causes include sexually transmitted infections (STIs) like chlamydia, systemic autoimmune diseases like lupus, and tuberculosis affecting the genitourinary system.
Next Steps and Follow-Up
The necessary follow-up for a 1+ leukocyte result depends heavily on whether the person is experiencing any symptoms. If a patient reports symptoms like painful urination, urinary urgency, or lower abdominal pain, a physician will typically order a urine culture and sensitivity test. The culture is the definitive test that identifies the exact type and quantity of bacteria present, confirming a true infection that requires specific antibiotic treatment.
If the 1+ finding is discovered incidentally in a person without any urinary symptoms, the physician may recommend repeating the urinalysis. This repeat test helps rule out sample contamination, provided a careful clean-catch technique is used for the second sample. If the 1+ result persists without symptoms, a doctor may investigate non-infectious causes, reviewing the patient’s medication history or checking for other signs of underlying inflammatory conditions.