04/08/2026
The tube shown is a lavender (purple) top EDTA Vacutainer. It contains K₂EDTA (dipotassium ethylenediaminetetraacetic acid) or sometimes K₃EDTA as an anticoagulant.
🩸 Hematological tests performed using an EDTA tube
Blood collected in this tube is commonly used for:
✅ Complete Blood Count (CBC/FBC)
✅ Hemoglobin (Hb)
✅ Hematocrit (Packed Cell Volume, PCV)
✅ Total White Blood Cell (WBC) count
✅ Differential WBC count
✅ Platelet count
✅ Red Blood Cell (RBC) count
✅ Red cell indices (MCV, MCH, MCHC, RDW)
✅ Peripheral Blood Film (Blood smear)
✅ Reticulocyte count
✅ Hemoglobin electrophoresis (in many laboratories)
✅ ESR (when using the EDTA method, depending on the laboratory protocol)
⭐ Unique characteristics of the EDTA tube
Cap color: 🟣 Lavender/Purple
Anticoagulant: K₂EDTA or K₃EDTA
Mechanism: Chelates (binds) calcium ions, preventing blood clotting.
Preserves cell morphology: Maintains the size and shape of RBCs, WBCs, and platelets, making it the anticoagulant of choice for hematology.
Mixing requirement: Gently invert the tube 8–10 times immediately after collection to ensure proper mixing.
Not suitable for: Coagulation tests (PT, APTT) or calcium-related chemistry tests because EDTA binds calcium and can interfere with results.
💡 PHARMK Fast Track Tip
🟣 Purple = Hematology = EDTA
Memory aid: "EDTA = Every Drop Tests the Blood Cells."
It preserves blood cells while preventing clot formation, making it the gold standard anticoagulant for routine hematological investigations.