CPT (Certified Phlebotomy Technician) Practice Exam

What is the purpose of serum separator tubes?

1. Separates platelets from the packed red blood cells

2. Keeps the sample sterile

3. Enhances hemolysis

4. Preserves white blood cells

The correct answer is: Separates platelets from the packed red blood cells

The purpose of serum separator tubes is primarily to separate the serum from the cellular components of the blood after centrifugation. When the blood is drawn into a serum separator tube, it contains a gel-like substance that, upon centrifugation, forms a barrier between the serum and the cells. This separation allows for easier collection and analysis of the serum, which is often required for various laboratory tests. While separating platelets from packed red blood cells is one component of this process, the main function is to isolate the serum itself for testing purposes. This ensures that the results obtained from serum analyses are accurate, as the serum carries the biochemical information needed for diagnosis and treatment evaluations. The other purposes mentioned do not align with the primary function of these tubes; they do not keep the sample sterile, they do not enhance hemolysis (in fact, they minimize it), and they do not preserve white blood cells, as the focus is on obtaining serum. Therefore, identifying the separation of serum from cells as a key aspect of the functionality of these tubes provides a clearer understanding.