Which anticoagulant is contained in a pink-lidded blood collection tube used for hematology testing?

• A. EDTA (ethylenediaminetetraacetic acid)
• B. Lithium heparin
• C. Sodium fluoride
• D. Acid citrate dextrose

Answer: (A)

The key idea is how anticoagulants keep blood from clotting so we can analyze its cells. The pink-lidded tube uses EDTA, which binds calcium ions and stops the clotting cascade. By preventing coagulation, EDTA preserves the shape and distribution of cells, making it ideal for hematology tests like complete blood counts and differential counts. Other additives serve different purposes: lithium heparin is used for certain plasma chemistry tests but can affect cell counts or morphology; sodium fluoride is a glycolysis inhibitor, not a reliable anticoagulant for hematology; and acid citrate dextrose is used for blood banking and some specialized studies.