A client has been admitted to the emergency department with suspected anaphylaxis following a bee sting. What laboratory finding supports this hypothesis.

Choice A rationale Eosinophils are leukocytes that are primarily involved in allergic reactions, asthma, and parasitic infections. An increase in eosinophils (eosinophilia) is a common finding during and after an anaphylactic reaction as these cells degranulate and release inflammatory mediators. Normal range is 1-4 percent of total white blood cells. Choice B rationale Neutrophils are the most abundant white blood cell, primarily responsible for fighting bacterial infections and inflammation. While they may increase in response to general stress, an increase in neutrophils (neutrophilia) is not a specific diagnostic marker for an acute allergic reaction or anaphylaxis. Normal range is 55-70 percent. Choice C rationale Monocytes are large white blood cells that differentiate into macrophages, playing a role in chronic inflammation and immune surveillance. An increase in monocytes (monocytosis) is not a specific finding for the acute, immediate hypersensitivity reaction that characterizes anaphylaxis. Normal range is 2-8 percent. Choice D rationale Basophils are granulocytes that contain histamine and other mediators central to anaphylaxis; their rapid degranulation and release of contents causes the symptoms. Consequently, the actual basophil count in the blood often decreases (basopenia) during an acute episode as they migrate to tissues and degranulate. Normal range is 0.5-1 percent.