Which tube type is typically used for plasma chemistry testing?

• A. Red-top tubes
• B. EDTA tubes
• C. Fluoride-oxalate tubes
• D. Heparin tubes

Answer: (D)

For plasma chemistry testing, you want a specimen that stays liquid and yields plasma without clotting, plus one that doesn’t interfere with the broad range of chemistry measurements. Heparin effectively prevents clotting while preserving plasma for analysis, making it the preferred anticoagulant for most chemistry panels. Red-top tubes produce serum after clotting, which changes the sample composition and can affect results. EDTA binds calcium and can skew electrolyte and enzyme measurements, so it’s better suited to hematology rather than chemistry. Fluoride-oxalate tubes contain oxalate and fluoride; oxalate chelates calcium and fluoride can interfere with enzymatic assays, so they’re not ideal for general plasma chemistry. So, the tube type used most for plasma chemistry testing is the one with heparin anticoagulant.