What does a red top tube contain?

The red top tube is specifically designed to contain no additives, making it ideal for collecting serum samples. This type of tube allows the blood drawn to clot naturally; after the clotting process, the sample can then be centrifuged to separate the serum from the cellular components. This feature is essential for various serum tests where a clear, serum sample is required. The absence of any additives in the red top tube ensures that the serum's stability for testing purposes is maintained, providing accurate results free from potential contamination or interference from agents that could alter the serum composition.

In contrast, other options describe tubes that either contain additives, such as anticoagulants or gel separators, which are not applicable to the red top tube. Understanding the function and composition of blood collection tubes is crucial for phlebotomists in order to select the appropriate tube for specific laboratory tests.