Which action does sodium fluoride provide when collecting plasma glucose specimens?

• A. Serves as a coenzyme of hexokinase
• B. Prevents reactivity of non-glucose reducing substances
• C. Precipitates proteins
• D. Inhibits glycolysis

Answer: (D)

When a blood sample sits for glucose testing, cells keep consuming sugar through glycolysis, which lowers the measured glucose if not slowed down. Sodium fluoride is used to prevent this, acting as an antiglycolytic agent. It specifically inhibits the glycolytic enzyme enolase, blocking a step in the pathway and thereby preserving the glucose level in the specimen for accurate measurement. It isn’t a coenzyme for hexokinase, it doesn’t target non-glucose reducing substances, and it doesn’t precipitate proteins. So the key action of sodium fluoride in plasma glucose collection is to inhibit glycolysis.