Which laboratory result is of most concern to you for an adult patient with cystitis?

• A. Serum white blood cell (WBC) count of 9000/ mm3
• B. Urinalysis results showing 1 or 2 WBCs present
• C. Urine bacteria count of 100,000 colonies per milliliter
• D. Serum hematocrit of 36%

Answer: (C)

In a suspected bladder infection, the most important lab sign is significant bacteria in the urine. A urine bacteria count of 100,000 colonies per milliliter indicates a substantial bacterial load consistent with an active urinary tract infection and would prompt treatment. The other results don’t point to a localized bladder infection or urgent systemic concern: a serum WBC count of 9,000/mm3 is normal and not specific to a bladder infection; a urinalysis showing only 1–2 WBCs suggests little or no pyuria and is not supportive of active infection; and a serum hematocrit of 36% isn’t informative for cystitis. Therefore, the urine bacteria count of 100,000 colonies per milliliter is the most concerning finding in this context.