On complete blood count, which finding suggests infectious or inflammatory disease?

• A. Leukocytosis with neutrophilia or neutropenia; left shift may be present
• B. Isolated anemia without leukocyte changes
• C. Eosinophilia without other signs
• D. Thrombocytosis only

Answer: (A)

The main idea is that the white blood cell response on a complete blood count reflects how the body handles infection or inflammation. A rise in white cells with a neutrophil predominance, and especially the presence of immature neutrophils in the blood (a left shift), points to infectious or inflammatory activity. Neutrophils are the first responders to bacterial challenges, so their numbers can surge (neutrophilia) or, in severe cases, drop (neutropenia) while the marrow pumps out more cells. When immature neutrophils appear in the circulation, it signals that the body is under stress from inflammation or infection and is rushing neutrophil production.

The other patterns don’t fit as well. Isolated anemia without changes in white cells doesn’t specifically indicate infection. Eosinophilia often points to allergic processes or parasitic infections rather than a general infectious/inflammatory state. Thrombocytosis can accompany inflammation too, but without the accompanying neutrophil response or left shift, it’s less diagnostic of an infectious/inflammatory process.