Final answer:
A lavender/purple top Vacutainer tube containing EDTA is most commonly used for CBC tests as EDTA prevents blood clotting, preserving blood cell morphology for accurate counting and analysis.
Step-by-step explanation:
A lavender/purple top Vacutainer tube that contains EDTA (ethylenediaminetetraacetic acid) is most commonly used for a CBC (Complete Blood Count), which is a blood test used to evaluate your overall health and detect a wide range of disorders, including anemia, infection, and leukemia.
EDTA acts as an anticoagulant, binding to calcium in the blood and preventing clotting, which makes it ideal for full blood counts and blood films, as the blood cells are kept intact.
In clinical practice, lavender top tubes are filled with blood which is then centrifuged to obtain plasma, and can be used for numerous analyses where the preservation of blood cell morphology is essential.