NHA Phlebotomy Certification Practice Exam

Which additive is commonly associated with the collection of a CBC?

1. Sodium citrate

2. EDTA

3. Heparin

4. Silica

The correct answer is: EDTA

The common additive associated with the collection of a complete blood count (CBC) is EDTA (ethylenediaminetetraacetic acid). EDTA works as an anticoagulant by binding calcium ions in the blood, which is essential for the clotting process. This property allows for the accurate counting of blood cells without the interference of clot formation that could occur if blood were allowed to coagulate. When blood is collected for a CBC, it is crucial that the sample remains in a liquid state so that automated analyzers can accurately measure the various components, such as red blood cells, white blood cells, and platelets. Because EDTA effectively prevents clotting, it ensures that the samples are suitable for these tests. While sodium citrate is also a type of anticoagulant, it is more commonly used for coagulation studies rather than a complete blood count. Heparin is another anticoagulant, but it is typically utilized in tests that require plasma and is not the standard for CBC. Silica, on the other hand, is a clot activator often used in serum collection but does not serve the purpose needed for CBC testing. Thus, EDTA is the correct additive for preserving the integrity of the blood sample for CBC evaluations