JLP Phlebotomy Practice Exam

Preserving cell morphology while preventing clotting is essential for accurate smear evaluation. EDTA chelates calcium, stopping the coagulation cascade, so the blood remains fluid and the cells stay intact. This maintains the true shapes and staining properties of the cells, which is crucial for a good peripheral blood smear. Other options either lack an anticoagulant (plain serum) or use anticoagulants that can alter cell appearance or interfere with staining (citrate or heparin), making them less ideal for smears. So, an EDTA tube is the best choice for samples requiring anticoagulation to preserve cells for smears.