What does a differential count evaluate in blood samples?

A differential count specifically evaluates the types of white blood cells (WBCs) present in a blood sample. This test is crucial in clinical settings as it provides valuable information about the immune response and can help identify various conditions and infections. A differential count categorizes the WBCs into different types, including neutrophils, lymphocytes, monocytes, eosinophils, and basophils, each of which plays a distinct role in the body's defense mechanisms. By analyzing the proportions of these cells, healthcare providers can gain insights into the patient's health status, such as whether there is an ongoing infection, an allergic reaction, or a hematologic disorder.

The other options focus on different aspects of blood components or characteristics—such as red blood cell counts, blood viscosity, or glucose levels—none of which pertain to the differential count specifically. This distinction highlights the focused purpose of the differential count in distinguishing between types of white blood cells rather than assessing overall blood characteristics or components.