Which statement correctly distinguishes lavender top and gray top tubes?

• A. Lavender top contains EDTA and is used for CBC; Gray top contains potassium oxalate and fluoride and is used for glucose testing
• B. Lavender top is used for serum chemistry; Gray top is for plasma electrolytes
• C. Lavender top contains citrate; Gray top contains heparin
• D. Lavender top is for coagulation testing; Gray top is for lipid profiling

Answer: (B)

The main idea is how the two tube types differ in their additives and the tests they’re intended for. Lavender-top tubes contain EDTA, which chelates calcium and prevents clotting. This preserves blood cells so they can be counted and examined, making lavender top the standard choice for hematology work like a complete blood count. Gray-top tubes combine potassium oxalate, another anticoagulant, with sodium fluoride, a glycolysis inhibitor. This setup keeps glucose from being broken down by cells after collection, which is essential for accurate glucose testing. So the distinction comes from the exact anticoagulant and the typical test purpose: lavender for cell- and hematology-based measurements, gray for glucose testing because it preserves glucose levels.

The other descriptions mix up these roles: lavender is not used for routine serum chemistry (which relies on serum obtained after clotting), and gray is not used generally for plasma electrolyte panels.