NHA Phlebotomy Certification Practice Exam

What type of tube is commonly used for a complete blood count?

1. Purple with clot activator

2. Lavender with EDTA

3. Lavender with NaK

4. Green with heparin

The correct answer is: Lavender with EDTA

The tube commonly used for a complete blood count (CBC) is the lavender tube containing EDTA (ethylenediaminetetraacetic acid). EDTA acts as an anticoagulant, which is essential for preserving the cellular components of blood for accurate analysis. The choice of EDTA is particularly beneficial because it effectively prevents clotting by binding calcium ions, which are necessary for the coagulation process. When performing a CBC, accurate counts of blood cells, including red blood cells, white blood cells, and platelets, are critical. The use of the lavender tube with EDTA ensures that the cells remain in their natural state, allowing for precise counting and reliable results during hematological assessments. Other tubes listed have different properties that do not support the requirements for a CBC. For instance, tubes with clot activators would promote clotting, while those containing heparin or other anticoagulants might not preserve cell morphology as effectively as EDTA. This is why the lavender tube with EDTA is the standard choice for this type of blood test.