American Medical Technologist (AMT) Practice Exam

The red top tube is primarily used for collecting serum samples because it does not contain any additives that would interfere with the analysis of the serum. When blood is drawn into a red top tube, it clots, and after a period of time, the clot retracts and separates the serum from the cellular components. This allows for the serum to be easily accessed for various laboratory tests, such as biochemical analyses, hormone levels, and serological tests.

In contrast, the other tube colors mentioned include additives that could hinder the analysis of serum. For instance, the green top tube typically contains heparin, which is an anticoagulant, and thus is used for plasma rather than serum. The blue top tube contains sodium citrate, which is also an anticoagulant and is primarily used for coagulation studies. The yellow top tube may contain either a gel separator or additives for specific types of testing, and is used for blood cultures or for tests requiring specific preservatives. Therefore, the red top tube is the most appropriate choice for obtaining a serum sample due to its specific design for clotting and serum separation.