CPT (Certified Phlebotomy Technician) Practice Exam

The grey top tube is specifically designed for tests that require the measurement of glucose levels and lactic acid concentration in the blood. This tube often contains sodium fluoride as an additive, which helps to inhibit glycolysis, the breakdown of glucose by cells. By preventing glycolysis, the tube ensures that the glucose levels in the specimen remain stable for accurate testing, especially important when checking for conditions like diabetes.

This use is particularly distinct compared to the other choices, as the grey top tube is not suitable for blood cultures, which typically require sterile collection techniques and different containment. Plasma separation is achieved using different tubes containing heparin as an anticoagulant, not the grey top tube. Lastly, while lipid profiles do have specific collection requirements, they are typically drawn in serum separator tubes, which are different from the grey top tubes intended for glucose and lactic acid testing.