Final answer:
The red-topped Vacutainer tube generally contains no additive and is used to allow blood to clot naturally for serum determinations and blood donor screening. The correct answer is option: 2) none
Step-by-step explanation:
The red-topped Vacutainer tube typically contains no additive. It is designed for serum determinations in chemistry and blood donor screening. It is important to note that other tube colors correspond to different additives.
For example, lavender-topped tubes usually contain EDTA, light blue ones are associated with sodium citrate, and tubes with additives for clotting will contain substances such as silica as a clot activator.
In the case of a red-topped tube, it is simply a plain vacuum tube that allows blood to clot naturally and is often used for serology and immunohematology tests.