CPT (Certified Phlebotomy Technician) Practice Exam

Sodium fluoride is a chemical additive commonly used in blood collection tubes to preserve glucose and inhibit glycolysis, making it essential for accurate glucose testing. The gray-top tube is specifically designed to contain sodium fluoride along with other preservatives, ensuring that blood samples for glucose analysis remain stable until testing can occur. This characteristic is crucial in laboratory settings where timely and accurate results are pivotal for patient care and diagnosis. In contrast, the other tube colors have different additives that serve various purposes. Red-top tubes typically contain no additives or may be used for serum testing. Green-top tubes usually contain heparin as an anticoagulant for plasma studies. Blue-top tubes contain sodium citrate and are primarily used for coagulation studies. Therefore, the presence of sodium fluoride specifically identifies the gray-top tube as the correct answer for this question.