NAVTA Practice Test 2025 – 400 Free Practice Questions to Pass the Exam

A red top tube is specifically designed for serum collection. When blood is drawn into this type of tube, it contains no anticoagulants, allowing the blood to clot. After the tube is spun in a centrifuge, the components of the blood separate based on density. The solid components (such as blood cells) settle at the bottom, while the liquid portion that remains above the clot is serum.

Serum is essentially the liquid part of blood that remains after coagulation, containing water, electrolytes, proteins, hormones, and waste products. This is why the correct answer is serum; it directly reflects what results from the blood collection and processing in a red top tube.

In contrast, plasma, found in tubes with anticoagulants, is collected before any clotting occurs, and whole blood retains all components together without separation. Platelets are a type of cell found within whole blood and are not specifically produced or isolated in the process of spinning a red top tube.