Which tube type is used to obtain serum after clotting?

• A. Serum Tubes
• B. EDTA Tubes
• C. Heparin Tubes
• D. Citrate Tubes

Answer: (A)

To get serum, you allow the blood to clot and then separate the liquid from the clot by centrifugation. The clotting factors (like fibrinogen) are consumed to form the clot, so the liquid portion that remains is serum, which lacks these clotting factors. Therefore the tube used is a serum tube, designed without anticoagulants to promote clotting (often red-top or serum separator tubes).

In contrast, tubes containing anticoagulants such as EDTA, heparin, or citrate prevent clotting, so they yield plasma after centrifugation rather than serum.