Which additive is present in grey top tubes used for glucose testing?

Which additive is present in grey top tubes used for glucose testing?

• A. Sodium citrate and potassium oxalate
• B. Sodium fluoride and potassium oxalate
• C. EDTA
• D. Lithium heparin

Answer: (B)

Preserving glucose levels in the sample is the main idea here. Grey top tubes use sodium fluoride and potassium oxalate. Sodium fluoride acts as a glycolysis inhibitor, slowing down the enzymatic breakdown of glucose after collection so the measured glucose stays accurate. Potassium oxalate serves as an anticoagulant to keep the blood from clotting, which is important for the chemistry analysis. The other additives are used for different tests: citrate with oxalate is not used for glucose testing and is associated with coagulation studies; EDTA is used for hematology tests in lavender-top tubes; lithium heparin in green-top tubes is common for many chemistry tests but does not inhibit glycolysis, so it isn’t ideal for glucose testing.

Preserving glucose levels in the sample is the main idea here. Grey top tubes use sodium fluoride and potassium oxalate. Sodium fluoride acts as a glycolysis inhibitor, slowing down the enzymatic breakdown of glucose after collection so the measured glucose stays accurate. Potassium oxalate serves as an anticoagulant to keep the blood from clotting, which is important for the chemistry analysis.

The other additives are used for different tests: citrate with oxalate is not used for glucose testing and is associated with coagulation studies; EDTA is used for hematology tests in lavender-top tubes; lithium heparin in green-top tubes is common for many chemistry tests but does not inhibit glycolysis, so it isn’t ideal for glucose testing.