CPT (Certified Phlebotomy Technician) Practice Exam 2026 - Free Certified Phlebotomy Technician Practice Questions and Study Guide

The correct answer is the one that identifies the primary use of the red tube, which is typically used for blood typing. Red tubes do not contain any anticoagulant, as they are designed to collect serum. This is crucial when blood is needed for serological tests, such as blood typing or crossmatching in the blood bank.

The absence of an anticoagulant in the red tube allows the blood sample to clot, enabling the serum to be separated from the cellular components after centrifugation, which is essential for various tests, particularly in the blood bank. This separation process is fundamental for accurate testing in immunohematology, where the identification of blood types is critical for transfusions.

Other choices incorrectly associate the red tube with tests or anticoagulants that do not apply. For example, the red tube does not contain anticoagulants and is not used for cardiac tests, a complete blood count (CBC), or stat chemistry tests which typically require different types of tubes with specific additives.