Which type of blood collection tube is known for clotting the blood sample quickly?

• A. Green-top tube
• B. Red-top tube
• C. Blue-top tube
• D. Purple-top tube

Answer: (B)

The type of blood collection tube known for clotting the blood sample quickly is the red-top tube. This tube is designed to contain no additives, allowing the blood to clot freely once collected. The absence of anticoagulants ensures that the blood will clot within a short amount of time, making it ideal for collecting serum samples for various laboratory tests.

In clinical settings, the red-top tube is particularly useful for tests that require serum analysis, such as hormone levels, viral serologies, and certain biochemical tests. The serum can then be easily separated from the clotted cells just by centrifugation.

In contrast, other tubes serve different purposes. For instance, the green-top tube contains heparin, an anticoagulant that prevents clotting, while the blue-top tube contains sodium citrate, which also acts as an anticoagulant specifically used for coagulation studies. The purple-top tube, on the other hand, contains EDTA, which is used primarily for complete blood counts (CBC) and other hematological studies, also preventing clotting.

Thus, the red-top tube's design facilitates rapid clotting, making it essential for specific tests that require serum.