Which statement correctly describes the role of anticoagulants in preparing plasma?

• A. Anticoagulants prevent blood from clotting to preserve plasma
• B. Anticoagulants promote fibrin formation
• C. Anticoagulants remove white cells
• D. Anticoagulants convert plasma to serum

Answer: (A)

Anticoagulants prevent blood from clotting, which keeps the liquid component of blood as plasma rather than letting it form a clot and become serum. By inhibiting the coagulation cascade (for example, by calcium chelation or inhibiting thrombin), they preserve fibrinogen and other clotting factors in the plasma. If the blood clots, the liquid obtained after centrifugation is serum, which lacks fibrinogen. So using an anticoagulant ensures you end up with plasma. The other statements describe actions opposite to this purpose or concepts not involved in plasma preparation.