Why is EDTA preferred for complete blood count testing?

• A. Preserves cell morphology and prevents coagulation by chelating calcium.
• B. Inhibits bacterial growth in the sample.
• C. Enhances clot formation.
• D. Increases hemolysis risk.

Answer: (A)

EDTA is used in CBC testing because it prevents clotting by binding calcium, a necessary factor for the coagulation cascade. This keeps the blood liquid so cells can be counted accurately and their shapes preserved, which is essential for reliable leukocyte differential counts and red cell indices. It also reduces platelet clumping, improving morphology. It’s not about antimicrobial action, it does not promote clotting, and when handled properly it doesn’t inherently increase hemolysis.