White blood count interpretation: Which indicates infection?

• A. Polys(high band %) -infection
• B. High WBC with neutrophilia
• C. Low platelets
• D. Lymphocytosis

Answer: (A)

A rise in band neutrophils (high band percentage) signals an acute bacterial infection. When the body responds, the bone marrow releases neutrophils to fight the invader, and many are immature, called bands. This left shift is a classic clue that the infection is active and bacterial, more specific than just counting total white blood cells.

A high WBC with neutrophilia can occur with infection, but it isn’t as specific as seeing bands released. Low platelets point to different issues like platelet disorders or other illnesses, not typically used to indicate infection. Lymphocytosis is more often seen with viral infections or certain conditions, not the classic picture of acute bacterial infection.