Which tube type and additive combination is typically used for plasma chemistry while minimizing fibrinogen presence?

• A. PST (Light Green) Top with Lithium Heparin and Gel (Plasma Chemistry)
• B. Red Top with No Additive
• C. Lavender Top with EDTA
• D. Gray Top with Sodium Fluoride

Answer: (A)

For plasma chemistry you want a clean plasma sample produced without clot formation and with minimal interference from cellular components. A Plasma Separation Tube that uses lithium heparin as the anticoagulant plus a gel separator delivers just that: the lithium heparin prevents clotting, so you get liquid plasma, and the gel creates a barrier between plasma and cells during centrifugation, helping to reduce cellular activation and contamination. This combination yields plasma with fewer interference factors, including a reduced contribution from fibrinogen, which is important for many chemistry assays.

The red-top tube has no additive and yields serum after clotting, which isn’t what you want for plasma chemistry. The lavender-top tube uses EDTA, which is great for hematology but can interfere with certain chemistry tests. The gray-top tube contains sodium fluoride with an oxalate anticoagulant and is aimed at glycolysis inhibition for glucose testing, not general plasma chemistry.