Why is a red-top tube used in some blood tests?

The red-top tube is commonly used in blood tests because it does not contain any additives, allowing the blood to clot naturally. Once clotting occurs, the tube can be centrifuged, thereby separating the serum from the cellular components of blood. The resultant serum can then be used for various laboratory tests, which require serum rather than whole blood. The design of the red-top tube facilitates this process by ensuring that the sample is free of anticoagulants, which would otherwise inhibit clotting and compromise the serum collection.

This feature makes it particularly suitable for tests where serum analysis is critical, such as in measuring certain biochemical substances, hormones, or medications. Understanding the function of the red-top tube in this context is essential for proper specimen handling and test accuracy.