Which of the following tubes contains an antiglycolytic agent?

The correct answer is the tube that contains sodium fluoride, as it serves as an antiglycolytic agent. This means it helps to preserve glucose levels in the blood by inhibiting glycolysis, the process by which glucose is broken down by cells. When blood is drawn, red blood cells and other components can continue to metabolize glucose if there are no inhibitors present, potentially leading to inaccurate glucose test results. Sodium fluoride effectively stops this metabolic process, making it vital for accurate glucose testing and commonly used in tests where glucose stability is crucial, such as during fasting glucose tests.

The PST tube with lithium heparin primarily serves as an anticoagulant, but it does not contain an antiglycolytic agent. While EDTA tubes are effective in preventing clotting and can preserve other components in blood samples, they do not contain substances aimed specifically at inhibiting glycolysis. The clear tube, often used for serum samples, does not have any additives that would prevent glycolysis either. Thus, the specific role of sodium fluoride in maintaining glucose levels makes the tube containing it the correct choice for this question.