Which laboratory finding would indicate increased infection risk due to methotrexate-related bone marrow suppression?

• A. Elevated neutrophils
• B. Neutropenia
• C. Thrombocytosis
• D. Polycythemia

Answer: (B)

Bone marrow suppression from methotrexate lowers white blood cell production, especially neutrophils. Neutrophils are the first line of defense against bacteria, so when their numbers drop (neutropenia), the body’s ability to fight infections wanes and infection risk rises. A low neutrophil count is the lab finding that signals this increased risk.

An elevated neutrophil count would suggest the opposite—an active response to infection rather than a risk from suppression. Thrombocytosis (high platelets) and polycythemia (high red blood cells) don’t specifically reflect infection risk due to marrow suppression. Monitoring typically involves a CBC with differential to track the neutrophil (ANC) levels.