What is the purpose and source of a peripheral smear?

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The main idea is that a peripheral smear is used to visually evaluate the shapes and appearances of blood cells, which helps identify abnormalities in red cells, white cells, and platelets that point to conditions like anemia, infections, or hematologic disorders. To prepare it, a small sample of whole blood collected in an EDTA-containing tube is spread thin on a glass slide, allowed to air dry, and then stained so cellular details are visible under a microscope. EDTA is chosen as the anticoagulant because it preserves cell morphology and prevents clotting, keeping the cells intact for accurate examination.

This is not about measuring chemical components—those tests use serum or plasma chemistry analytes. It’s also not prepared from plasma to view platelets; plasma lacks intact cells, and the smear’s value lies in observing the morphology of all blood cells in anticoagulated whole blood. And it isn’t a test for glucose measurement, which relies on plasma or serum chemistry.