What is the primary use of fluoride-oxalate tubes in clinical pathology?

• A. CBC
• B. Serum chemistry
• C. Urinalysis
• D. Plasma glucose testing and glycolysis inhibition

Answer: (D)

Fluoride-oxalate tubes are designed to preserve glucose in blood samples by preventing glycolysis while also preventing clotting to obtain plasma. The fluoride component slows or stops glycolysis by inhibiting the enzyme enolase, so cells won’t continue consuming glucose after collection. The oxalate acts as an anticoagulant by binding calcium, keeping the blood from clotting and allowing plasma to be separated for testing. This combination makes the tube ideal for plasma glucose determination because it keeps the glucose level from dropping after the sample is drawn. Other tubes are used for different purposes—CBC typically requires a different anticoagulant to preserve blood cell morphology, serum chemistry uses a tube that allows clotting to yield serum, and urinalysis uses a urine sample with its own handling requirements.