Step 1: Understanding the Concept:
Following blood collection, red blood cells continue to metabolize glucose via glycolysis, which artificialy decreases the measured glucose concentration over time.
To obtain an accurate reading, an agent must be used that inhibits glycolysis in addition to preventing coagulation.
Step 3: Detailed Explanation:
- Sodium fluoride acts as an antiglycolytic agent by inhibiting enolase, a key enzyme in the glycolytic pathway. It is commonly paired with potassium oxalate (an anticoagulant) in clinical gray-top blood collection tubes.
- EDTA and Sodium citrate prevent coagulation by chelating calcium ions but do not halt cellular glycolysis.
- Heparin acts by activating antithrombin III to inhibit coagulation pathways but does not affect glycolytic enzymes.
Step 4: Final Answer
The agent used to preserve blood samples for glucose estimation is sodium fluoride.