Which statement describes the role of EDTA in preserving sample quality?

• A. They preserve cell morphology and prevent clotting
• B. They preserve serum enzymes
• C. They promote clot formation for many tests
• D. They change cell color

Answer: (A)

EDTA acts as an anticoagulant by chelating calcium, which is essential for the blood clotting process. By removing calcium, coagulation is inhibited, so the blood remains un-clotted and the cells stay intact. This preservation of cell morphology is crucial for accurate hematology tests, such as white blood cell and platelet counts and peripheral smears. EDTA tubes are designed to yield plasma (not serum), and while they keep cells well-preserved, they’re not used to preserve serum enzymes; some enzyme tests require serum or can be affected by calcium chelation. EDTA’s role is not to promote clotting or to change cell color, but specifically to prevent clotting and maintain cell integrity for reliable cell-based analyses.