Which statement about a serum gel tube is true?

• A. It does not contain anticoagulant.
• B. It contains anticoagulant.
• C. It is used for CBC testing.
• D. It contains a gel separator.

Answer: (A)

Serum gel tubes are designed to yield serum, which requires blood to clot. Because clotting is needed, these tubes do not contain an anticoagulant. After the sample clots and is centrifuged, a gel separator may be present to keep serum apart from the clot and cells. If an anticoagulant were present, the blood would not clot and you’d obtain plasma instead of serum, which is why this tube isn’t used for tests that require serum. CBC testing uses whole blood with anticoagulant, so a serum tube isn’t appropriate for that purpose. The gel separator is common in many serum gel tubes, but the key point for this statement is the absence of anticoagulant.