NHA Phlebotomy Certification Practice Exam

What is the key difference between plasma and serum?

1. Serum contains fibrinogen

2. Serum is from a non-clotted specimen

3. Plasma is from a clotted specimen

4. Plasma contains fibrinogen

The correct answer is: Plasma contains fibrinogen

Plasma and serum are both components of blood, but they differ significantly in their composition and the processes used to obtain them. Plasma is the liquid portion of blood that remains after the blood has been treated with anticoagulants to prevent clotting. It retains all of the clotting factors, including fibrinogen, which is essential for blood coagulation. In contrast, serum is obtained from blood that has clotted; it is the liquid that remains after the clot has formed and the clotting factors have been used up in the process. As a result, serum does not contain fibrinogen, as this protein is consumed in the clotting process when the blood coagulates. Therefore, the statement that plasma contains fibrinogen accurately highlights one of the essential distinctions between the two. Understanding this difference is crucial for phlebotomy practice, as the type of specimen collected will determine which tests can be performed and how results may be interpreted in a clinical setting.