Which urinalysis finding strongly suggests a urinary tract infection?

• A. Pyuria (WBCs) and bacteriuria
• B. Nitrites only
• C. Leukocyte esterase only
• D. Positive culture alone

Answer: (A)

When evaluating a suspected urinary tract infection on urinalysis, the strongest clue is finding both white blood cells in the urine (pyuria) and bacteria present in the urine (bacteriuria). Pyuria shows the inflammatory response from the urinary tract fighting infection, while bacteriuria confirms that bacteria are actually in the urinary tract. Together, they provide the most specific indication of an active infection rather than just irritation or contamination.

Nitrites can be helpful because many common UTI bacteria convert nitrates to nitrites, but not all pathogens do this, and a negative nitrite result doesn’t rule out infection. Leukocyte esterase indicates white blood cells but can be positive in noninfectious inflammation or with sample contamination, making it less specific. A positive culture confirms bacterial growth, but culture results alone don’t reflect the immediate inflammatory activity visible on the urinalysis and can occur in asymptomatic bacteriuria or contaminated samples. Therefore, the combination of pyuria and bacteriuria on urinalysis most strongly points to a urinary tract infection.