Which laboratory finding most clearly indicates an infection?

Which laboratory finding most clearly indicates an infection?

• A. WBC 15,000 mm3
• B. ESR 15 mm/hr
• C. Urine pH 7.2
• D. Urine specific gravity 1.0063

Answer: (A)

An infection prompts the immune system to release and mobilize more white blood cells, causing leukocytosis. A white blood cell count of 15,000/mm3 is above the normal range and is the clearest sign of an infectious process among the options. The erythrocyte sedimentation rate is a nonspecific marker of inflammation and can be elevated for many reasons beyond infection; a value around 15 mm/hr is not strongly indicative of infection by itself. Urine pH and urine specific gravity are not direct indicators of infection—the pH can vary with diet and metabolism, and specific gravity reflects urine concentration rather than infection status.

An infection prompts the immune system to release and mobilize more white blood cells, causing leukocytosis. A white blood cell count of 15,000/mm3 is above the normal range and is the clearest sign of an infectious process among the options.

The erythrocyte sedimentation rate is a nonspecific marker of inflammation and can be elevated for many reasons beyond infection; a value around 15 mm/hr is not strongly indicative of infection by itself. Urine pH and urine specific gravity are not direct indicators of infection—the pH can vary with diet and metabolism, and specific gravity reflects urine concentration rather than infection status.