If a laboratory test requires serum, which Vacutainer tube is the tube of choice?

When a laboratory test specifically requires serum, the tube that is used should be one that allows for the biological sample to clot, separating the serum from the cellular components of the blood. The red-topped tube is designed for this purpose as it does not contain any anticoagulants that would prevent clotting. When blood is drawn into a red-topped tube, it coagulates, forming a clot that allows the serum to be collected after centrifugation.

In contrast, the other options contain additives that either prevent clotting or are intended for different types of analyses. The green-topped tube contains heparin, an anticoagulant that would prevent clot formation and therefore would not yield serum. The yellow-topped tube is typically used for specific tests, such as blood culture or certain immunological tests, and may contain additives like sodium polyanethol sulfonate (SPS) that also inhibit clotting. The lavender-topped tube contains EDTA, which is another anticoagulant that binds calcium, preventing clotting and thus is not suitable for serum collection.

In summary, the red-topped tube is the preferred choice for obtaining serum, as it allows the blood to clot and separates the serum after centrifugation, making it ideal for