CPT (Certified Phlebotomy Technician) Practice Exam

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What chemical additive is in a red tube?

Lithium Heparin
Sodium Citrate
Silicone
Sodium Heparin

The correct answer is: Silicone

The correct choice related to the chemical additive in a red tube is actually not Silicone, as red-top tubes are typically used for serum collection and do not have any additive. They are designed to clot the blood, allowing the serum to be separated after centrifugation. Lithium Heparin is an anticoagulant found in green-topped tubes, and Sodium Citrate is used in light blue-topped tubes for coagulation studies. Sodium Heparin is typically paired with green tubes as well. Thus, the presence of a specific chemical additive is why the red tube is known for its role in serum collection rather than containing any of the additives listed in the alternatives. In summary, the red tube is characterized by the absence of additives, which promotes the clotting of blood for serum analysis.