For a client with idiopathic thrombocytopenic purpura (ITP), which laboratory finding is expected to be decreased?

In the context of idiopathic thrombocytopenic purpura (ITP), the hallmark feature of this condition is a significant decrease in platelet counts. ITP is characterized by an autoimmune response where the body's immune system mistakenly attacks and destroys platelets, leading to thrombocytopenia (low platelet count).

As platelets are essential for normal blood clotting, a decrease in their numbers directly contributes to the symptoms of the condition, such as easy bruising, bleeding, and petechiae. Laboratory tests in patients with ITP would consistently show low platelet levels, which aligns with the nature of the disease.

In contrast, white blood cells (WBC), red blood cells (RBC), and granulocytes are not primarily affected in ITP. While these cell lines can fluctuate in various conditions affecting bone marrow or systemic disease processes, ITP specifically does not lead to a decreased production of these blood components directly. Therefore, the expected and defining laboratory finding in a patient with ITP is a decrease in platelets.