Which additive in lavender-top tubes is commonly used for hematology testing?

• A. EDTA
• B. Sodium Citrate
• C. Heparin
• D. Sodium Fluoride

Answer: (C)

Lavender-top tubes use EDTA as the additive. EDTA works as an anticoagulant by chelating calcium, which prevents blood from clotting and preserves the shape and integrity of blood cells. This preservation is essential for accurate complete blood counts and other hematology measurements, since it keeps cells stable and minimizes aggregation. Other additives, like heparin (green-top) or sodium citrate (blue-top), serve different purposes and aren’t the standard choice for routine hematology testing.