What are the signs of a urinary tract infection (UTI) in a urine test?

From the Guidelines

A urinary tract infection (UTI) is typically diagnosed through a urine test that shows several key abnormalities, including the presence of leukocyte esterase and nitrites in the urine, as well as pyuria, hematuria, and bacteriuria under microscopic examination, as noted in the most recent study 1. The most significant signs of a UTI in a urine test include:

• Leukocyte esterase (indicating white blood cells)
• Nitrites (produced by many bacteria that cause UTIs)
• Pyuria (increased white blood cells)
• Hematuria (blood in urine)
• Bacteriuria (bacteria in urine) A positive urine culture with bacterial growth of >100,000 organisms per milliliter, as mentioned in 1, confirms the infection. Other findings may include:
• Cloudy or foul-smelling urine
• Abnormal pH (often more alkaline)
• Occasionally protein in the urine These laboratory findings, combined with symptoms like painful urination, frequency, and urgency, help healthcare providers diagnose UTIs accurately. For definitive diagnosis, the urine culture identifies the specific bacteria causing the infection and determines which antibiotics will be most effective for treatment, as stated in the latest guideline 1.

From the Research

Signs of UTI in Urine Test

The signs of a urinary tract infection (UTI) in a urine test can be identified through various methods, including:

• Dipstick urinalysis: This method is popular for its availability and usefulness, but results must be interpreted in context of the patient's pretest probability based on symptoms and characteristics 2.
• Nitrites: Nitrites are likely more sensitive and specific than other dipstick components for UTI, particularly in the elderly 2.
• Leukocyte esterase: This test can detect the presence of white blood cells in the urine, which can indicate a UTI 3, 4.
• Microscopic urinalysis: This method is likely comparable to dipstick urinalysis as a screening test 2.
• Bacteriuria: Bacteriuria is more specific and sensitive than pyuria for detecting UTI, even in older women and during pregnancy 2.
• Pyuria: Pyuria is commonly found in the absence of infection, particularly in older adults with lower urinary tract symptoms such as incontinence 2.

Diagnostic Accuracy of Urine Tests

The diagnostic accuracy of urine tests for UTI can vary, with:

• Gram staining showing 56.9% sensitivity and 76.8% specificity 3.
• Leukocyte esterase having 67.9% sensitivity and 84.5% specificity 3.
• Nitrite demonstrating the highest sensitivity (85.3%) 3.
• The combination of Gram staining, leukocyte esterase, and nitrite achieving 87.6% sensitivity and 94.6% negative predictive value (NPV) 3.

Limitations of Urine Tests

It's important to note that:

• A positive dipstick urinalysis did not reliably detect significant bacteriuria in women with suspected uncomplicated UTI 4.
• Urine culture is still the gold standard for detection of UTI, and should be performed in cases where the probability of UTI is moderate or unclear 2.