Which value represents the optimal EDTA concentration?

• A. 0.5 mg/mL
• B. 3 mg/mL
• C. 1.0 mg/mL
• D. 1.5 mg/mL

Answer: (D)

EDTA is used as an anticoagulant in hematology because it chelates calcium, stopping the coagulation cascade. The final EDTA concentration in blood must be enough to prevent clotting without disturbing cell integrity. Around 1.5 mg/mL in whole blood is the standard that provides reliable anticoagulation while preserving cell morphology for accurate CBC results. Too little EDTA risks clot formation and invalid results; too much can cause subtle cellular changes or artifacts that skew counts. So, 1.5 mg/mL represents the best balance for maintaining sample quality and test accuracy.